Playback apparatus and method, program, recording medium, data structure, and manufacturing method for recording medium

ABSTRACT

A playback apparatus includes an obtaining unit obtaining playback management information including a main playback path of a main stream set, a first sub playback path of a first sub-stream set, and a second sub playback path of a second sub-stream set. The first and second sub playback paths are allowed for a predetermined category. A selection-receiver receives a selection of streams as a first combination or a second combination. A reading unit reads the corresponding stream sets according to whether the first or second combination is selected. A playback unit plays back the main stream set and the first or second sub-stream set. The number of files that are readable at one time is predetermined. The sub playback paths are determined so that the number of the files that are readable at one time does not exceed the predetermined number.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a division of application Ser. No. 11/505,370, filedAug. 17, 2006, and claims the benefit of priority under 35 U.S.C. §119from Japanese Patent Application JP 2005-250163 filed in the JapanesePatent Office on Aug. 30, 2005 and Japanese Patent Application JP2006-156203 filed in the Japanese Patent Office on Jun. 5, 2006, theentire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to playback apparatuses andmethods, programs, recording media, data structures, and manufacturingmethods for recording media. More particularly, the invention relates toa playback apparatus and method, a program, a recording medium, a datastructure, and a manufacturing method for the recording medium, whichare suitably used when playing back streams.

2. Description of the Related Art

In digital versatile disc (DVD) video standards, interactive operationscan be performed, that is, users can switch sound or subtitles whenplaying back AV content, such as a movie, recorded in an informationrecording medium (for example, see DVD Specifications for Read-Only DiscPart 3; Version 1.1). More specifically, in a display device 1 shown inFIG. 1, the user operates a sound switch button 11 or a subtitle switchbutton 12 of a remote controller 2 to switch sound or subtitles of AVcontent displayed on the display device 1. For example, if the useroperates the sound switch button 11 when sound 1 is set in the initialstate in the display device 1, sound 1 is switched to sound 2, as shownin FIG. 2.

AV content based on the DVD video standards is recorded in the form of aMoving Picture Experts Group (MPEG)2 program stream. In the MPEG2program stream, as shown in FIG. 3, a video stream (indicated by “video”in FIG. 3), a plurality of audio streams (indicated by “audio 1”, “audio2”, and “audio 3” in FIG. 3), and a plurality of sub-picture streams(indicated by “sub-picture 1, “sub-picture 2”, and “sub-picture 3”) aremultiplexed such that the audio streams and the sub-picture streams aresynchronized with the video stream. The sub-picture streams(sub-pictures 1, 2, and 3) are streams in which bitmap images arerun-length coded, and are mainly used for subtitles.

Generally, a plurality of audio streams are used for recording sound ofdifferent languages, and a plurality of sub-picture streams are used forrecording subtitles of different languages. The user can interactivelyselect sound or subtitles of a desired language by using the remotecontroller 2 while video is being played back.

The DVD video standards define a table structure, provided to users,indicating the relationship between sound numbers and a plurality ofaudio streams (audio 1, 2, and 3) and the relationship between subtitlenumbers and a plurality of sub-picture streams (sub-pictures 1, 2, and3) in a program stream.

FIG. 4 illustrates an example of such a stream number table. In thistable, the sound numbers are referred to as “A_SN (Audio StreamNumbers)”, and the subtitle numbers are referred to as “S_SN(Sub-picture Stream Numbers)”. In the stream number table shown in FIG.4, each of the audio streams is provided with A_SN, and morespecifically, A_SN=1: audio 2, A_SN=2: audio 1, and A_SN-3: audio 3.Also in FIG. 4, each of the sub-picture streams is provided with S_SN,and more specifically, S_SN=1: sub-picture 3, S_SN=2: sub-picture 1, andS_SN=3: sub-picture 2. In this case, a smaller number of A_SN or S_SNindicates an audio signal or a subtitle signal to be provided to userswith higher priority. That is, A_SN=1 is an audio stream played back asa default, and S SN=1 is a sub-picture stream played back as a default.

More specifically, sound 1 played back in the initial state in FIG. 1 isaudio 2, which is A_SN=1 (FIG. 4), and sound 2 played back after beingswitched from sound 1 in FIG. 2 is audio 1, which is A_SN=2.

SUMMARY OF THE INVENTION

According to the DVD video standards, however, when the user switchessound or subtitles while playing back a video program stream, the usercan select only from audio streams or sub-picture streams multiplexedinto the program stream which is currently played back. That is, whenplaying back the MPEG2 program stream shown in FIG. 3, the user canselect only from audio 1 through audio 3 when switching sound.

Accordingly, even if another stream having audio streams and subtitlesdifferent from a program stream which is currently played back isavailable, it is difficult for the user to switch sound or subtitles tothe audio streams or subtitles in the different stream. Accordingly, theextensibility in selecting streams is low.

It can also be considered that in the near future, content to beswitched will not be restricted to sound, but will be extended tovarious types of content items, such as video. If it is difficult toselect content items from a stream different from a stream which isbeing played back when switching such various types of content, theextensibility in selecting streams becomes low.

It is thus desirable to simplify the data structure of various types ofcontent, such as sound and video, that can be selected from streams ordata files different from a main AV stream so that the selected contentcan be played back together with the main AV stream.

According to an embodiment of the present invention, there is provided aplayback apparatus including obtaining means for obtaining playbackmanagement information including a main playback path indicating aposition on a time axis of a main stream set, a first sub playback pathindicating a position on the time axis of a first sub-stream set, and asecond sub playback path indicating a position on the time axis of asecond sub-stream set, which is different from the first sub-stream set,the playback management information being classified into apredetermined category among a plurality of categories that are definedbeforehand in accordance with the type of the main stream set, theplayback management information satisfying at least a first conditionthat each of the first sub playback path and the second sub playbackpath is a playback path allowed for the predetermined category,selection-receiving means for receiving a selection of streams to beplayed back based on the playback management information obtained by theobtaining means as a first combination of the main stream set and thefirst sub stream set or a second combination of the main stream set andthe second sub stream set, reading means for reading the main stream setby referring to the main playback path and the first sub-stream set byreferring to the first sub playback path when the selection of the firstcombination is received by the selection-receiving means, or for readingthe main stream set by referring to the main playback path and thesecond sub-stream set by referring to the second sub playback path whenthe selection of the second combination is received by theselection-receiving means, and playback means for playing back, togetherwith the main stream set read by the reading means, the first sub-streamset or the second sub-stream set read by the reading means. The mainstream set, the first sub-stream set, and the second sub-stream set areincluded in files. The number of the files that are readable at one timeby the reading means is a predetermined number. The playback managementinformation satisfies, in addition to the first condition, a secondcondition that one or more of the first and second sub playback pathsare determined so that the number of the files that are readable at onetime does not exceed the predetermined number.

The main playback path may indicate a position on the time axis of atleast one stream of the main stream set included in a first file. Thefirst sub playback path or the second sub playback path may indicate aposition on the time axis of at least one stream of the first sub-streamset or the second sub-stream set, respectively, included in one or moresecond files. The reading means may read one or more streams specifiedby the playback management information obtained by the obtaining meansfrom a corresponding file selected from the first file referred to bythe main playback path and the one or more second files referred to byone or more of the first and second sub playback paths.

The predetermined number of the files that are readable at one time maybe two. The first file and the one or more second files may be differentfiles, and the second condition may be that the one or more first andsecond sub playback paths are determined so that the number of thesecond file read together with the first file is one.

The predetermined number of the files that are readable at one time maybe two. Among the one or more second files, a predetermined second filemay be the same file as the first file, and the remaining file may be afile different from the first file. The second condition may be that theone or more sub-playback paths are determined so that one of the secondfiles read with the first file is the same file as the first file andthe other second file is different from the first file.

If the one or more first and second sub playback paths include at leastone non-synchronized reading type defining that the one or more secondfiles are read asynchronously with the first file, the playbackmanagement information may satisfy, in addition to the first conditionand the second condition, a third condition that the one or more secondfiles referred to by the one or more first and second sub playback pathsof the non-synchronized reading type do not count toward the number ofthe files that are readable at one time.

According to another embodiment of the present invention, there isprovided a playback method or a program including the steps of obtainingplayback management information including a main playback pathindicating a position on a time axis of a main stream set, a first subplayback path indicating a position on the time axis of a firstsub-stream set, and a second sub playback path indicating a position onthe time axis of a second sub-stream set, which is different from thefirst sub-stream set, the playback management information beingclassified into a predetermined category among a plurality of categoriesthat are defined beforehand in accordance with the type of the mainstream set, the playback management information satisfying at least afirst condition that each of the first sub playback path and the secondsub playback path is a playback path allowed for the predeterminedcategory, receiving a selection of streams to be played back based onthe obtained playback management information as a first combination ofthe main stream set and the first sub stream set or a second combinationof the main stream set and the second sub stream set, reading the mainstream set by referring to the main playback path and the firstsub-stream set by referring to the first sub playback path when theselection of the first combination is received, or for reading the mainstream set by referring to the main playback path and the secondsub-stream set by referring to the second sub playback path when theselection of the second combination is received, and playing back,together with the read main stream set, the first sub-stream set or thesecond sub-stream set which is read. The main stream set, the firstsub-stream set, and the second sub-stream set are included in files. Thenumber of the files that are readable at one time is a predeterminednumber. The playback management information satisfies, in addition tothe first condition, a second condition that one or more of the firstand second sub playback paths are determined so that the number of thefiles that are readable at one time does not exceed the predeterminednumber.

Data or a data structure recorded on a recording medium according to anembodiment of the present invention includes playback managementinformation for managing playback of at least two streams including afirst stream and a second stream. The playback management informationincludes a main playback path indicating the position on the time axisof the first stream, a sub playback path indicating the position on thetime axis of the second stream, and type information indicating whetherthe second stream is played back synchronously with the first stream andwhether the second stream is multiplexed into the same file as the firststream.

The type information may indicate that the second stream is played backsynchronously with the first stream and that the second stream ismultiplexed into the same file as the first stream.

The type information may indicate that the second stream is played backsynchronously with the first stream and that the second stream ismultiplexed into a file different from a file of the first stream.

The type information may indicate that the second stream is played backasynchronously with the first stream and that the second stream ismultiplexed into a file different from a file of the first stream.

According to another embodiment of the present invention, there isprovided a manufacturing method for a recording medium on which datathat can be played back by a playback apparatus is recorded. Themanufacturing method includes the steps of generating data having a datastructure including playback management information for managingplayback of at least two streams, the playback management informationincluding a main playback path indicating the position on the time axisof the first stream, a sub playback path indicating the position on thetime axis of the second stream, and type information indicating whetherthe second stream is played back synchronously with the first stream andwhether the second stream is multiplexed into the same file as the firststream, and recording the generated data on the recording medium.

Data or a data structure recorded on a recording medium according toanother embodiment of the present invention includes playback managementinformation for managing playback of a file including at least onestream. Playback management information includes a main playback pathindicating the position on the time axis of a main stream set, a firstsub playback path indicating the position on the time axis of a firstsub-stream set, and a second sub playback path indicating the positionon the time axis of a second sub-stream set, which is different from thefirst sub-stream set, the playback management information beingclassified into a predetermined category among a plurality of categoriesthat are defined beforehand in accordance with the type of the mainstream set. The playback management information at least satisfies acondition that each of the first sub playback path and the second subplayback path is a playback path allowed for the predetermined category.The main stream set, the first sub-stream set, and the second sub-streamset are included in files. The first sub playback path and the secondsub playback path are determined so that the number of the files thatare readable at one time does not exceed a number which is predeterminedin a playback apparatus.

According to another embodiment of the present invention, there isprovided a manufacturing method for a recording medium on which datathat can be played back by a playback apparatus is recorded. Themanufacturing method includes the steps of generating data having a datastructure including playback management information and recording thegenerated data on the recording medium. In the data structure, playbackmanagement information includes a main playback path indicating theposition on the time axis of a main stream set, a first sub playbackpath indicating a position on the time axis of a first sub-stream set,and a second sub playback path indicating the position on the time axisof a second sub-stream set, which is different from the first sub-streamset, the playback management information being classified into apredetermined category among a plurality of categories that are definedbeforehand in accordance with the type of the main stream set. Theplayback management information at least satisfies a condition that eachof the first sub playback path and the second sub playback path is aplayback path allowed for the predetermined category. The main streamset, the first sub-stream set, and the second sub-stream set areincluded in files. The first sub playback path and the second subplayback path are determined so that the number of the files that arereadable at one time does not exceed a number which is predetermined inthe playback apparatus.

According to an embodiment of the present invention, various types ofcontent, such as sound and video, can be selected from streams or datafiles different from a main AV stream. In particular, the data structureof such content can be simplified, and the selected content can beplayed back.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate known sound switching operations;

FIG. 3 illustrates the structure of an MPEG2 program stream;

FIG. 4 illustrates a stream number table indicating sound signals andsubtitle signals provided to a user;

FIG. 5 illustrates an example of an application format on a recordingmedium installed on a playback apparatus of an embodiment of the presentinvention;

FIG. 6 illustrates the structure of a playlist including a main path andsub-paths;

FIG. 7 illustrates an example of a main path and a sub-path;

FIG. 8 illustrates another example of a main path and a sub-path;

FIG. 9 illustrates the syntax of PlayList( );

FIG. 10 illustrates the syntax of SubPath( );

FIG. 11 illustrates an example of SubPath_type;

FIG. 12 illustrates the syntax of SubPlayItem(i);

FIG. 13 illustrates the syntax of PlayItem( );

FIG. 14 illustrates the syntax of a first example of STN_table( );

FIG. 15 illustrates an example of the syntax of stream_entry( );

FIG. 16 illustrates the syntax of stream_attribute( );

FIG. 17 illustrates stream_coding_type;

FIG. 18 illustrates video_format;

FIG. 19 illustrates frame_rate;

FIG. 20 illustrates aspect_ratio;

FIG. 21 illustrates audio_presentation_type;

FIG. 22 illustrates sampling_frequency;

FIG. 23 illustrates character code;

FIG. 24 illustrates a stream number table indicating sound signals andsubtitle signals provided to a user;

FIG. 25 is a block diagram illustrating an example of the configurationof a playback apparatus according to an embodiment of the presentinvention;

FIGS. 26, 27, and 28 are flowcharts illustrating playback processingperformed by the playback apparatus shown in FIG. 25;

FIG. 29 is a flowchart illustrating processing in response to aninstruction to switch sound for audio stream #1 from a user;

FIG. 30 is a flowchart illustrating processing in response to aninstruction to switch sound for audio stream #2 from a user;

FIG. 31 is a flowchart illustrating details of step S60 in FIG. 29;

FIG. 32 illustrates an example in which two audio streams are mixed andplayed back;

FIG. 33 illustrates the syntax of a second example of STN_table( )defining combinations of audio streams #1 and audio streams #2;

FIG. 34 illustrates an example of the bitmap syntax ofCombination_of_Primary_and_Secondary;

FIG. 35 illustrates a stream number table indicating sound signals andsubtitle signals provided to a user;

FIG. 36 illustrates another example in which two audio streams are mixedand played back;

FIG. 37 illustrates the syntax of a third example of STN_table( )defining combinations of audio streams #1 and audio streams #2;

FIG. 38 illustrates the syntax of a fourth example of STN_table( )defining combinations of audio streams #1 and audio streams #2;

FIG. 39 illustrates a picture-in-picture (PiP) technique;

FIGS. 40 and 41 illustrate the syntax of a fifth example of STN_table( )defining combinations of secondary video streams, primary audio streams,secondary audio streams, and subtitle streams that can be played backtogether with primary video streams;

FIG. 42 illustrates a stream number table indicating combinations ofsound signals, video signals, and subtitle signals provided to a user;

FIG. 43 illustrates a user selection operation for selecting acombination of a secondary video stream, a primary audio stream, asecondary audio stream, and a subtitle stream that can be played backtogether with a primary video stream;

FIG. 44 illustrates a playlist generated by using SubPath_type shown inFIG. 11 to implement the picture-in-picture technique;

FIG. 45 illustrates another example of SubPath_type different fromSubPath_type shown in FIG. 11;

FIG. 46 illustrates another example of stream_entry( );

FIGS. 47 and 48 illustrate examples of playlists generated by usingSubPath_type shown in FIG. 45 to implement the picture-in-picturetechnique;

FIG. 49 is a block diagram illustrating another example of theconfiguration of a playback apparatus according to an embodiment of thepresent invention;

FIGS. 50 and 51 are flowcharts illustrating secondary video switchingprocessing performed by the playback apparatus shown in FIG. 49;

FIG. 52 illustrates the categories of application_type;

FIG. 53 illustrates a sub-path restriction technique, and morespecifically, FIG. 53 illustrates sub-paths that can be provided forplaylists according to the types of playlists;

FIG. 54 illustrates a sub-path restriction technique, and morespecifically, FIG. 54 illustrates the relationships between the numberof play items disposed in a playlist and the number of sub-paths;

FIGS. 55 through 58 illustrate specific examples of playlists generatedby the sub-path restriction technique shown in FIGS. 53 and 54;

FIGS. 59 and 60 are flowcharts illustrating playback processing for aplaylist having application_type=3;

FIGS. 61 through 64 are flowcharts illustrating playback processing fora playlist having application_type=1 or 2;

FIGS. 65 and 66 illustrate a manufacturing method for a recording mediumon which data to be played back by an playback apparatus of anembodiment of the present invention is recorded; and

FIG. 67 illustrates the configuration of a personal computer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing an embodiment of the present invention, thecorrespondence between the features of the claims and an embodiment ofthe present invention is discussed below. This description is intendedto assure that the embodiment supporting the claimed invention isdescribed in this specification. Thus, even if an element in thefollowing embodiment is not described as relating to a certain featureof the present invention, that does not necessarily mean that theelement does not relate to that feature of the claims. Conversely, evenif an element is described herein as relating to a certain feature ofthe claims, that does not necessarily mean that the element does notrelate to other features of the claims.

Furthermore, this description should not be construed as restrictingthat all the aspects of the invention disclosed in the embodiment aredescribed in the claims. That is, the description does not deny theexistence of aspects of the present invention that are described in theembodiment but not claimed in the invention of this application, i.e.,the existence of aspects of the present invention that in future may beclaimed by a divisional application, or that may be additionally claimedthrough amendments.

A playback apparatus (for example, a playback apparatus 401 shown inFIG. 49) according to an embodiment of the present invention includesobtaining means (controller 34 shown in FIG. 49 executing step S11 inFIG. 26 for playing back a playlist of application_type=1 or 2 shown inFIGS. 61 through 64) for obtaining playback management information (forexample, the playlist shown in FIG. 58) including a main playback path(for example, the main path shown in FIG. 58) indicating a position on atime axis of a main stream set (for example, video or audio in clip AVstream-0 in FIG. 58), a first sub playback path (for example, sub-path 1in FIG. 58) indicating a position on the time axis of a first sub-streamset (for example, second video or second audio), and a second subplayback path (for example, sub-path 2 referring to clip AV stream-1 orsub-path 3 referring to clip AV stream-2) indicating a position on thetime axis of a second sub-stream set (for example, audio), which isdifferent from the first sub-stream set, the playback managementinformation being classified into a predetermined category (for example,a category, i.e., movie-type/time-based slideshow of categoriesclassified into application_type (of main TS) in FIG. 53, that is,synchronized type, which is discussed below) among a plurality ofcategories that are defined beforehand in accordance with the type ofthe main stream set, the playback management information satisfying atleast a first condition that each of the first sub playback path and thesecond sub playback path is a type (for example, one of SubPath_type(FIG. 45)=5, 6, or 7 in FIG. 53) of playback path allowed for thepredetermined category, selection-receiving means (for example, thecontroller 34 shown in FIG. 49 executing steps S164 through S169) forreceiving a selection of streams to be played back based on the playbackmanagement information obtained by the obtaining means as a firstcombination of the main stream set and the first sub stream set or asecond combination of the main stream set and the second sub stream set,reading means (for example, the controller 34 shown in FIG. 49 executingprocessing equivalent to step S108 in FIG. 51 before executing step S151in FIG. 62, step S155 in FIG. 63, and steps S161 and S162 in FIG. 64when playing back the playlist in FIG. 58) for reading the main streamset by referring to the main playback path and the first sub-stream setby referring to the first sub playback path when the selection of thefirst combination is received by the selection-receiving means, or forreading the main stream set by referring to the main playback path andthe second sub-stream set by referring to the second sub playback pathwhen the selection of the second combination is received by theselection-receiving means, and playback means (for example, an AVdecoder 33 shown in FIG. 49 executing step S151 in FIG. 62, step S155 inFIG. 63, and steps S161 and S162 in FIG. 64) for playing back, togetherwith the main stream set read by the reading means, the first sub-streamset or the second sub-stream set read by the reading means. The mainstream set, the first sub-stream set, and the second sub-stream set areincluded in files (clips). The number of the files that are readable atone time by the reading means is a predetermined number. The playbackmanagement information satisfies, in addition to the first condition, asecond condition (for example, the number of sub paths in FIG. 53 andthe conditions shown in FIG. 54) that one or more of the first andsecond sub playback paths are determined so that the number of the filesthat are readable at one time does not exceed the predetermined number.

The main playback path indicates a position on the time axis of at leastone stream (for example, clip AV stream-0 in FIGS. 55 through 58) in themain stream set included in a first file. The first sub playback path orthe second sub playback path indicates a position on the time axis of atleast one stream (for example, clip AV stream-1, 2, 3 in FIGS. 55through 58) in the first sub-stream set or the second sub-stream set,respectively, included in one or more second files, and the readingmeans reads one or more streams specified by the playback managementinformation obtained by the obtaining means from a corresponding fileselected from the first file referred to by the main playback path andthe one or more second files referred to by one or more of the first andsecond sub playback paths.

The predetermined number of the files that are readable at one time istwo. The first file and the one or more second files are different files(for example, in FIGS. 55 through 57, the clips containing clip AVstream-1, 2, 3 are different from the clip containing clip AV stream-0).The second condition is that the one or more first and second subplayback paths are determined so that the number of the second file readtogether with the first file is one (for example, the middle row in thetable shown in FIG. 54).

The predetermined number of the files that are readable at one time istwo. Among the one or more second files, a predetermined second file isthe same file as the first file (for example, in FIG. 58, a clip, whichis the second file including the clip AV stream referred to by subpath-1, is the same clip as the first file referred to by the mainpath), and the remaining files are files different from the first file(for example, in FIG. 58, clips, which are the second files referred toby sub-path 2 and sub-path 3, are clip-1 and clip-2 different fromclip-0, which is the first file referred to by the main path). Thesecond condition is that the one or more sub playback paths aredetermined so that one of the second files read with the first file isthe same file as the first file or the other second file is differentfrom the first file (for example, the bottommost row in the table shownin FIG. 54).

If the one or more first and second sub playback paths include at leastone non-synchronized reading type (for example, in FIG. 45,SubPath_type=3, i.e., IG preloading type) defining that the one or moresecond files are read asynchronously with the first file, the playbackmanagement information satisfies, in addition to the first condition andthe second condition, a third condition that the one or more secondfiles referred to by the one or more first and second sub playback pathsof the non-synchronized reading type do not count toward the number ofthe files that are readable at one time.

A playback method or a program according to another embodiment of thepresent invention includes the steps of obtaining playback managementinformation (for example, the playlist shown in FIG. 58) including amain playback path (for example, the main path shown in FIG. 58)indicating a position on a time axis of a main stream set (for example,video or audio of clip-0 in FIG. 58), a first sub playback path (forexample, sub-path 1 in FIG. 58) indicating a position on the time axisof a first sub-stream set, and a second sub playback path (for example,sub-path 2 referring to clip AV stream-1 shown in FIG. 58 and sub-path 3referring to clip AV stream-2) indicating a position on the time axis ofa second sub-stream set (for example, audio), which is different fromthe first sub-stream set, the playback management information beingclassified into a predetermined category (for example, a category, i.e.,movie-type/time-based slideshow of categories classified intoapplication_type (of main TS) in FIG. 53, that is, synchronized type,which is discussed below) among a plurality of categories that aredefined beforehand in accordance with the type of the main stream set,the playback management information satisfying at least a firstcondition that each of the first sub playback path and the second subplayback path is a type (for example, one of SubPath_type (FIG. 45)=5,6, or 7 in FIG. 53) of playback path allowed for the predeterminedcategory (for example, step S11 in FIG. 26 executed for playing back theplaylist of application_type=1 or 2), receiving a selection of streamsto be played back based on the obtained playback management informationas a first combination of the main stream set and the first sub streamset or a second combination of the main stream set and the second substream set (for example, steps S164 through S169 in FIG. 64), readingthe main stream set by referring to the main playback path and the firstsub-stream set by referring to the first sub playback path when theselection of the first combination is received, or for reading the mainstream set by referring to the main playback path and the secondsub-stream set by referring to the second sub playback path when theselection of the second combination is received (processing equivalentto step S108 in FIG. 51 before executing step S151 in FIG. 62, step S155in FIG. 63, and steps S161 and S162 in FIG. 64 when playing back theplaylist shown in FIG. 58), and playing back, together with the readmain stream set, the first sub-stream set or the second sub-stream setwhich is read (for example, step 151 in FIG. 62, step S155 in FIG. 63,and steps S161 and S162 in FIG. 64 when playing back the playlist inFIG. 58). The main stream set, the first sub-stream set, and the secondsub-stream set are included in files (clips). The number of the filesthat are readable at one time is a predetermined number. The playbackmanagement information satisfies, in addition to the first condition, asecond condition (for example, the number of sub paths in FIG. 53 andthe conditions shown in FIG. 54) that one or more of the first andsecond sub playback paths are determined so that the number of the filesthat are readable at one time does not exceed the predetermined number.

A data structure or data recorded on a recording medium according to anembodiment of the present invention includes playback managementinformation (for example, the playlist shown in FIG. 58) for managingplayback of at least two streams including a first stream and a secondstream. The playback management information includes a main playbackpath (for example, the main path in FIG. 58) indicating a position on atime axis of the first stream, a sub playback path (for example,sub-path 1 in FIG. 58) indicating a position on the time axis of thesecond stream, and type information (for example, SubPath_type=7 in FIG.45) indicating whether the second stream is played back synchronouslywith the first stream and whether the second stream is multiplexed intothe same file as the first stream.

A manufacturing method for a recording medium according to an embodimentof the present invention includes the steps of generating data having adata structure including playback management information (for example,the playlist shown in FIG. 58) for managing playback of at least twostreams, and recording the generated data on the recording medium. Theplayback management information includes a main playback path (forexample, the main path in FIG. 58) indicating a position on a time axisof the first stream, a sub playback path (for example, sub-path 1 inFIG. 58) indicating a position on the time axis of the second stream,and type information (for example, SubPath_type=7) indicating whetherthe second stream is played back synchronously with the first stream andwhether the second stream is multiplexed into the same file as the firststream.

The type information indicates that the second stream is played backsynchronously with the first stream and that the second stream ismultiplexed into the same file as the first stream (for example,SubPath_type=7).

The type information indicates that the second stream is played backsynchronously with the first stream and that the second stream ismultiplexed into a file different from a file of the first stream (forexample, SubPath_type=5).

The type information indicates that the second stream is played backasynchronously with the first stream and that the second stream ismultiplexed into a file different from a file of the first stream (forexample, SubPath_type=6).

Data or a data structure recorded on a recording medium according toanother embodiment of the present invention includes playback managementinformation. The playback management information includes a mainplayback path indicating a position on a time axis of a main stream set,a first sub playback path indicating a position on the time axis of afirst sub-stream set, and a second sub playback path indicating aposition on the time axis of a second sub-stream set, which is differentfrom the first sub-stream set, the playback management information beingclassified into a predetermined category among a plurality of categoriesthat are defined beforehand in accordance with the type of the mainstream set. The playback management information at least satisfies acondition that each of the first sub playback path and the second subplayback path is a type (for example, one of SubPath_type (FIG. 45)=5,6, or 7 in FIG. 53) of playback path allowed for the predeterminedcategory. The main stream set, the first sub-stream set, and the secondsub-stream set are included in files (clips). The first sub playbackpath and the second sub playback path are determined so that the numberof the files that are readable at one time does not exceed a numberwhich is predetermined in a playback apparatus.

A manufacturing method for a recording medium according to anotherembodiment of the present invention includes the steps of generatingdata having a data structure including playback management informationand recording the generated data on the recording medium. In the datastructure, playback management information includes a main playback pathindicating a position on a time axis of a main stream set, a first subplayback path indicating a position on the time axis of a firstsub-stream set, and a second sub playback path indicating a position onthe time axis of a second sub-stream set, which is different from thefirst sub-stream set, the playback management information beingclassified into a predetermined category among a plurality of categoriesthat are defined beforehand in accordance with the type of the mainstream set. The playback management information at least satisfies acondition that each of the first sub playback path and the second subplayback path is a type (for example, one of SubPath_type (FIG. 45)=5,6, or 7 in FIG. 53) of playback path allowed for the predeterminedcategory. The main stream set, the first sub-stream set, and the secondsub-stream set are included in files (clips). The first sub playbackpath and the second sub playback path are determined so that the numberof the files that are readable at one time does not exceed a numberwhich is predetermined in the playback apparatus.

An embodiment of the present invention is described below with referenceto the accompanying drawings.

FIG. 5 illustrates an example of an application format on a recordingmedium installed in a recording apparatus configured in accordance withan embodiment of the present invention, for example, a playbackapparatus 20 described below with reference to FIG. 25 or a playbackapparatus 401 described below with reference to FIG. 49. The recordingmedium is an optical disc, a magnetic disk, or a semiconductor memory,which is discussed below.

The application format has two layers, i.e., a playlist layer and a cliplayer, for managing AV streams. In this case, a pair of one AV streamand one item of clip information associated with the AV stream areconsidered to be as one object, which is referred to as a “clip”. An AVstream is also referred to as an “AV stream file”. The AV stream filemay include, not only sound data and video data, but also various streamfiles played back together with the sound data and the video data. Clipinformation is also referred to as a “clip information file”.

Generally, files used in computers are handled as byte strings. On theother hand, content of AV stream files is expanded onto a time axis, andaccess points in clips are mainly specified by playlists by using timestamps. That is, it can be said that the playlists and clips form twolayers for managing AV streams.

If access points in clips are indicated by playlists by using timestamps, a clip information file is used for finding, from the timestamps, information concerning an address at which decoding in an AVstream file is started.

A playlist is a set of playback zones of an AV stream. One playback zonein an AV stream is referred to as a “play item”, which is indicated by apair of an IN point (playback start point) and an OUT point (playbackend point) on the time axis. Accordingly, a playlist has one or aplurality of play items, as shown in FIG. 5.

In FIG. 5, the first playlist from the left has two play items, whichrefer to the first half and the second half of the AV stream containedin the clip at the left side in FIG. 5. The second playlist from theleft has one play item, which refers to the entirety of the AV streamcontained in the clip at the right side. The third playlist from theleft has two play items, which refer to a certain portion of the AVstream contained in the clip at the left side and a certain portion ofthe AV stream contained in the clip at the right side.

If a disc navigation program shown in FIG. 5 designates the left playitem contained in the first playlist from the left as informationconcerning the current playback position, the first half of the AVstream contained in the left clip, which is referred to by thedesignated play item, is played back. In this manner, the playlists areused as playback management information for managing the playbackoperation of AV stream files.

The disc navigation program has a function of controlling the playbackorder specified in playlists and interactive playback operations byusing playlists. The disc navigation program also has a function ofdisplaying a menu screen for allowing a user to give instructions toperform various types of playback operations. The disc navigationprogram is described in a programming language, for example, Java™, andis recorded on a recording medium.

In this embodiment, a playback path including at least one play item(sequential play items if there are more than one) in a playlist isreferred to as a “main path”, and a playback path including at least onesub-play item (may be sequential or non-sequential play items if thereare more than one) disposed in parallel with the main path in a playlistis referred to as a “sub-path”. That is, the application format on arecording medium installed in the playback apparatus 20 shown in FIG. 25or the playback apparatus 401 shown in FIG. 49 has at least onesub-path, which is played back in association with the main path, in aplaylist.

FIG. 6 illustrates the structure of the main path and sub-paths. Aplaylist is allowed to have the single main path and at least onesub-path. The main path includes at least one play item, and onesub-path includes at least one sub-play item.

The playlist shown in FIG. 6 has one main path including three playitems and three sub-paths. The play items forming the main path areprovided with IDs (identifications) from the head. More specifically,the main path includes play items, such as PlayItem_id=0, PlayItem_id=1,and PlayItem_id=2. The sub-paths are also provided with IDs from thehead. Subpath_id=0 has one sub-play item, Subpath_id=1 has two sub-playitems, and Subpath_id=2 has one sub-play item.

The stream referred to by the sub-play item contained in Subpath_id=0is, for example, dubbed Japanese movie sound, and can be played backinstead of the audio stream contained in the AV stream file referred toby the main path. The stream referred to by the sub-play items containedin Subpath_id=1 is, for example, Director's Cut, and can be insertedinto a predetermined portion of the AV stream file referred to by themain path as the director's commentaries.

A clip AV stream file referred to by one play item includes at leastvideo stream data (main image data). The clip AV stream file may alsoinclude at least one audio stream, which is played back simultaneouslywith (in synchronization with) the video stream (main image data) whichis also contained in the clip AV stream file. The clip AV stream filemay also include at least one bitmap subtitle stream file which isplayed back in synchronization with the video stream which is alsocontained in the clip AV stream file. The clip AV stream file may alsoinclude at least one interactive graphics stream file which is playedback in synchronization with the video stream which is also contained inthe clip AV stream file. The video stream contained in the clip AVstream file and the audio stream, bitmap subtitle stream, or interactivegraphics stream, which is played back in synchronization with the videostream, are multiplexed. In other words, a clip AV stream file referredto by one play item includes video stream data and at least 0 audiostream data, at least 0 bitmap subtitle stream data, or at least 0interactive graphics stream data, which is played back insynchronization with the video stream data, such that they aremultiplexed into the clip AV stream file.

That is, a clip AV stream file referred to by one play item includes aplurality of types of streams, such as a video stream, an audio stream,a bitmap subtitle stream, or an interactive graphics stream.

A sub-play item refers to, for example, audio stream data or subtitledata contained in a stream file different from the clip AV stream filereferred to by the play item.

When playing back a playlist including only a main path, the user canselect sound and subtitles only from audio streams and sub-picturestreams multiplexed into a clip referred to by that main path. Incontrast, when playing back a playlist including a main path and asub-path, the user can refer to audio streams and sub-picture streamsmultiplexed into a clip referred to by the sub-play item in addition toaudio streams and sub-picture streams multiplexed into a clip AV streamfile referred to by the main path.

As discussed above, at least one sub-path is included in one playlist,and a sub-play item of each sub-path refers to the correspondingstreams. Accordingly, AV streams having high extensibility and highflexibility can be provided. That is, sub-play items can be addedafterwards to the clip AV stream referred to by the main path.

FIG. 7 illustrates an example of a main path and an example of asub-path. In FIG. 7, an audio playback path played back simultaneouslywith (in synchronization with) the main path is indicated by using thesub-path.

The playlist shown in FIG. 7 includes one play item, i.e.,PlayItem_id=0, as the main path, and one sub-play item as the sub-path.PlayItem( ) which is PlayItem_id=0, refers to the main AV stream shownin FIG. 7. SubPlayItem( ) includes the following data. SubPlayItem( )includes Clip_Information_file_name for specifying the clip referred toby the sub-path in the playlist. In the example in FIG. 7, the sub-playitem refers to an auxiliary audio stream of SubClip_entry_id=0.SubPlayItem( ) also includes SubPlayItem_IN_time andSubPlayItem_OUT_time for specifying the playback zone of the sub-pathcontained in the designated clip (in this case, the auxiliary audiostream). SubPlayItem( ) also includes sync_PlayItem_id andsync_start_PTS_of_PlayItem for specifying the time at which the playbackoperation of the sub-path is started on the time axis of the main path.In FIG. 7, sync_PlayItem_id=0 and sync_start_PTS_of_PlayItem=t1. Withthis information, the time t1 at which the playback operation of thesub-path is started on the time axis of PlayItem=0 of the main path canbe specified. That is, in the example in FIG. 7, the playback start timeof the main path and the playback start time of the sub-path is thesame, i.e., t1.

The clip AV audio stream referred to by the sub-path should not includesystem time base (STC) non-sequential points. The clip audio sampleclock used for the sub-path is locked to the audio sample clock used forthe main path.

In other words, SubPlayItem( ) includes information for specifying theclip referred to by the sub-path, information for specifying theplayback zone of the sub-path, and information for specifying the timeat which the playback operation of the sub-path is started on the timeaxis of the main path. Since the clip AV stream used for the sub-pathdoes not include STC, the user can refer to a clip AV audio streamdifferent from the clip AV stream (main AV stream) referred to by themain path on the basis of the information included in SubPlayItem( ) andplays back the clip AV audio stream.

As stated above, the play item and the sub-play item individually manageclip AV stream files. The clip AV stream file (main AV stream file)managed by the play item is different from the clip AV stream filemanaged by the sub-play item.

In a manner similar to the example shown in FIG. 7, a subtitle streamplayback path played back simultaneously with the main path may beindicated by using a sub-path.

FIG. 8 illustrates another example of a main path and another example ofsub-paths. In FIG. 8, an audio playback path played back simultaneouslywith the main path is indicated by using a sub-path. The main AV streamfile referred to by the play item of the main path is similar to that inFIG. 7, and an explanation thereof is thus omitted.

It is now assumed that the clip AV stream referred to by the main pathis movie content (AV content), and the auxiliary audio stream referredto by the audio playback path of the sub-path is director's commentarieson that movie, and then, the auxiliary audio stream referred to by thesub-path is mixed into (overlaps with) the clip AV audio stream referredto by the main path. In this case, the configuration shown in FIG. 8 canbe used. More specifically, the configuration shown in FIG. 8 can beused when the user inputs an instruction to listen to the director'scommentaries on the movie into a player while watching the movie, forexample, when the auxiliary audio stream referred to by the sub-path ismixed into the sound of the clip AV stream referred to by the main path.

In FIG. 8, three play items, i.e., PlayItem_id=0, PlayItem_id=1, andPlayItem_id=2, are disposed in the main path, and two sub-play items aredisposed in the sub-path (Subpath_id=0). The sub-play item (discussedbelow with reference to FIG. 12) called by the sub-path (Subpath_id=0)(discussed below with reference to FIG. 10) includes SubPlayItem_IN_timeand SubPlayItem_OUT_time for specifying the playback zones of theauxiliary audio streams (English auxiliary audio stream clip havingSubClip_entry_id=0 and Japanese auxiliary audio stream clip havingSubClip_entry_id=1) of the sub-path.

Comparing the example in FIG. 8 with that in FIG. 7, it can be seenthat, in the example in FIG. 8, a sub-play item can refer to theauxiliary audio stream (English or Japanese audio stream) havingSubClip_entry_id=0 or SubClip_entry_id=1. That is, the use of thesub-play item makes it possible to refer to a plurality of audiostreams, and when playing back the sub-play item, an audio stream filecan be selected from a plurality of audio stream files, i.e., in theexample in FIG. 8, the English audio stream file or the Japanese audiostream file is selected. More specifically, one of SubClip_entry_id=0and SubClip_entry_id=1 is selected based on, for example, an instructionfrom the user, and the auxiliary audio stream referred to by theselected ID is played back. If an instruction to play back the auxiliaryaudio stream together with the audio stream referred to by the main pathis provided (for example, if an instruction to play back two audiostreams together), an audio stream referred to by the main path and anaudio stream referred to by the sub-path are mixed and played back.

The data structure (syntax) that implements the structure of the mainpath and sub-paths discussed with reference to FIGS. 6 through 8 is asfollows.

FIG. 9 illustrates the syntax of PlayList( ).

The length field is a 32-bit unsigned integer indicating the number ofbytes from immediately after the length field to the end of PlayList( )i.e., a field indicating the number of bytes fromreserved_for_future_use to the end of PlayList( ). After the lengthfield, the 16-bit reserved_for-future-use field follows. Thenumber_of_PlayItems is a 16-bit field indicating the number of playitems contained in the playlist. In the case of the example in FIG. 6,the number of play items is three, and the numeric value is assigned tothe play items as PlayItem_id from 0 in the order in which PlayItem( )appears in the playlist. For example, PlayItem_id=0, 1, 2 are assigned,as shown in FIGS. 6 and 8.

The number_of_SubPath is a 16-bit field indicating the number ofsub-paths (number of entries) contained in the playlist. In the case ofthe example in FIG. 6, the number of sub-paths is three, and the numericvalue is assigned to the sub-play items as SubPath_id from 0 in theorder in which SubPath( ) appears in the playlist. For example,Subpath_id=0, 1, 2 are assigned, as shown in FIG. 6. Then, in thesubsequent FOR statement, the play items are referred to for the samenumber of times as the number of play items, and the sub-paths arereferred to for the same number of times as the number of sub-paths.

FIG. 10 illustrates the syntax of SubPath( ).

The length field is a 32-bit unsigned integer indicating the number ofbytes from immediately after the length field to the end of PlayList( ),i.e., a field indicating the number of bytes fromreserved_for_future_use to the end of PlayList( ). After the lengthfield, the 16-bit reserved_for_future_use field follows. TheSubPath_type is an 8-bit field indicating the type of application of thesub-path, i.e., the type of sub-path, such as audio, bitmap subtitle, ortext subtitle. An example of the SubPath_type is discussed below withreference to FIG. 11. After the SubPath_type, the 15-bitreserved_for_future_use field follows. The is_repeat_SubPath field is aone-bit field indicating the playback method for the sub-path, and morespecifically, indicating whether the sub-path is played back repeatedlyor only once while playing back the main path. This field is used when,for example, the playback timing of the clip specified by the sub-pathis different from that of the main AV stream (when, for example, themain path is a still-image slideshow and the audio sub-path isbackground music (BGM) of the main path). After the is_repeat_SubPathfield, the 8-bit reserved_for_future_use follows. Thenumber_of_SubPlayItems is an 8-bit field indicating the number ofsub-play items (number of entries) contained in one sub-path. Forexample, the number of sub-play items of SubPath_id=0 in FIG. 6 is one,and the number of sub-play items of SubPath_id=1 is 2. In the subsequentFOR statement, the sub-play items are referred to for the same number oftimes as the number of sub-play items.

The SubPath_type (sub-path type) is disclosed in, for example, FIG. 42of Japanese Unexamined Patent Application Publication No. 2002-158965 or2002-158972. In those publications, however, only one sub-path type isdefined, and by the use of such SubPath_type, it is difficult toimplement various processing operations and techniques described aboveor described below. In this embodiment, therefore, the SubPath_typeshown in FIG. 11 or 45 is used.

Before explaining the SubPath_type shown in FIG. 45, the SubPath_typeshown in FIG. 11 is defined.

FIG. 11 illustrates an example of the SubPath_type. The types ofsub-paths can be defined, for example, as shown in FIG. 11.

In FIG. 11, SubPath_type=0 and SubPath_type=1 are reserved. TheSubPath_type=2 is the audio presentation path of the browsableslideshow. In SubPath_type=2, the audio presentation path referred to bythe sub-path is not synchronized with the main path referred to by theplay items in the playlist.

The SubPath_type=3 is the interactive graphics presentation menu. InSubPath_type=3, the interactive graphics presentation menu referred toby the sub-path is not synchronized with the main path referred to bythe play items in the playlist.

The SubPath_type=4 is the text subtitle presentation path. InSubPath_type=4, the text subtitle presentation path referred to by thesub-path is synchronized with the main path referred to by the playitems in the playlist.

The SubPath_type=5 is the second audio presentation path (which is thepath for referring to the second audio stream). In SubPath_type=5, thesecond audio presentation path referred to by the sub-path issynchronized with the main path referred to by the play items in theplaylist. The second audio stream referred to by that sub-path is, forexample, director's commentaries (sound) on a movie. For the sub-pathrepresented by Subpath_id=0 in FIG. 8, the SubPath_type isSubPath_type=5 in FIG. 10.

The SubPath_type=6 is the second video presentation path (which is thepath for referring to the second video stream). In SubPath_type=6, thesecond video presentation path referred to by the sub-path issynchronized with the main path referred to by the play items in theplaylist. The second video stream referred to by that sub-path is, forexample, director's commentaries (moving pictures) on a movie.

The SubPath_type=7 through SubPath_type=255 are reserved.

FIG. 12 illustrates the syntax of SubPlayItem(i).

The length field is a 16-bit unsigned integer indicating the number ofbytes from immediately after the length field to the end of SubPlayItem().

In FIG. 12, the syntax is divided into two portions, and morespecifically, a portion where the sub-play item refers to one clip and aportion where the sub-play item refers to a plurality of clips areshown.

The portion where the sub-play item refers to one clip is discussedfirst.

The SubPlayItem( ) includes Clip_Information_file_name[0] for specifyingthe clip, Clip_codec_identifier[0] for specifying the codec method forthe clip, reserved_for_future_use, is_multi_Clip_entries, which is aflag indicating whether multi-clips are registered, andref_to_STC_id[0], which is information concerning the STC non-sequentialpoints (non-sequential points of the system time base). If the flag ofis_multi_Clip_entries is ON, the syntax of the portion whereSubPlayItem( ) refers to a plurality of clips is checked. TheSubPlayItem( ) also includes SubPlayItem_IN_time andSubPlayItem_OUT_time for specifying the playback zone of the sub-pathcontained in the clip, and sync_PlayItem_id andsync_start_PTS_of_PlayItem for specifying the playback start time atwhich the playback operation of the sub-path is started on the time axisof the main path. The sync_PlayItem_id and sync_start_PTS_of_PlayItemare used when the playback timing of the main AV stream is the same asthat of the stream contained in the file referred to by the sub-path, asshown in FIGS. 7 and 8, but are not used when the playback timing of themain AV stream is different from the file referred to by the sub-path(for example, still-image slideshow (main path) is not synchronized withBGM (sub-path) for the slideshow). The SubPlayItem_IN_time,SubPlayItem_OUT_time, sync_PlayItem_id, and sync_start_PTS_of_PlayItemare used in common for the clip referred to by SubPlayItem( ).

Next, the portion where the sub-play item refers to a plurality of clips(if (is_multi_Clip_entries==1b), as in the case shown in FIG. 8, isdiscussed.

The num_of_Clip_entries indicates the number of clips, and designatesclips other than those havingClip_Information_file_name[0][SubClip_entry_id]. That is,num_of_Clip_entries designates clips, such as those havingClip_Information_file_name [1], Clip_Information-file-name [2], and soon, other than those having Clip_Information-file-name[0]. TheSubPlayItem( ) also includes Clip_codec_identifier[SubClip_entry_id] forspecifying the codec method for the clip,ref_to_STC_id[SubClip_entry_id], which is information concerning the STCnon-sequential points, and reserved_for_future_use.

The SubPlayItem_IN_time, SubPlayItem_OUT_time, sync_PlayItem_id, andsync_start_PTS_of_PlayItem are used in common for the clips referred toby SubPlayItem( ). In the example in FIG. 8, SubPlayItem_IN_time,SubPlayItem_OUT_time, sync_PlayItem_id, and sync_start_PTS_of_PlayItemare used in common for SubClip_entry_id=0 and SubClip_entry_id=1. Thetext-based subtitle for the selected SubClip_entry_id is played backbased on the SubPlayItem_IN_time, SubPlayItem_OUT_time,sync_PlayItem_id, and sync_start_PTS_of_PlayItem.

The numeric value is sequentially assigned to SubClip_entry_id from 1 inthe order in which Clip_Information_file_name[SubClip_entry_id] in theSubPlayItem( ) appears. The SubClip_entry_id ofClip_Information_file_name[0] is 0.

FIG. 13 illustrates the syntax of PlayItem( ).

The length field is a 16-bit unsigned integer indicating the number ofbytes from immediately after the length field to the end of PlayItem( ).Clip_Information_file_name[0] is a field for specifying the clipreferred to by PlayItem( ). In the example in FIG. 7, the main AV streamis referred to by Clip_Information_file_name[0]. The PlayItem( ) alsoincludes Clip_codec_identifier[0] specifying the codec method for theclip, reserved_for_future_use, is_multi_angle, connection_condition, andref_to_STC_id[0], which is information concerning the STC non-sequentialpoints. The PlayItem( ) also includes IN_time and OUT_time forspecifying the playback zone of the play item in the clip. In theexample in FIG. 7, IN_time and OUT_time specify the playback zone of themain clip AV stream file. The PlayItem( ) also includes UO_mask_table(), PlayItem_random_access_mode, and still_mode. A description of a casewhere is_multi_angle indicates a plurality of angles is not given here,since such a case is not directly related to the present invention.

The STN_table( ) provides a mechanism for allowing a user, if the targetplay item and at least one sub-path to be played back in associationwith the target play item are provided, to select from the streamscontained in the clip referred to by the play item and the clipsreferred to by at least sub-path when the user switches sound orsubtitles. The STN_table( ) provides a mechanism for allowing a user toimplement mixing playback by selecting two audio streams.

FIG. 14 illustrates an example of the syntax of STN_table( ) (firstSTN_table( )). The first STN_table( ) is set as an attribute ofPlayItem( ). The STN_table( ) is set as the attributes of a play item.

The length field is a 16-bit unsigned integer indicating the number ofbytes from immediately after the length field to the end of STN_table(). After the length field, a 16-bit reserved_for_future_use fieldfollows. The number_of_video_stream_entries indicates the number ofstreams provided with video_stream_id entered (registered) in STN_table(). The video_stream_id is information for identifying the video streams.The video_stream_number is the video stream number that can be seen bythe user when switching video.

The number_of_audio_stream_entries indicates the number of first audiostreams provided with audio_stream_id entered (registered) in STN_table(). The audio_stream_id is information for identifying the audio streams.The audio_stream_number is the audio stream number that can be seen bythe user when switching sound. The number_of_audio_stream2_entriesindicate the number of second audio streams provided withaudio_stream_id2 entered in the STN_( ). The audio_stream_id2 isinformation for identifying the second audio streams. Theaudio_stream_number is the audio stream number that can be seen from theuser when switching sound. More specifically, the audio streamsrepresented by number_of_audio_stream_entries entered in the STN-table() are audio streams decoded by the first audio decoder 75-1 of theplayback apparatus 20 shown in FIG. 25 or the playback apparatus 401shown in FIG. 49, which are discussed below. The audio streamsrepresented by number_of_audio_stream2_entries entered in the thirdSTN_table( ) are audio streams decoded by the second audio decoder 75-2of the playback apparatus 20 shown in FIG. 25 or the playback apparatus401 shown in FIG. 49. In this manner, in the STN_table( ) shown in FIG.14, two types of audio streams decoded by the two decoders can beentered.

The audio streams represented by number_of_audio_stream_entries decodedby the first audio decoder 75-1 of the playback apparatus 20 or 401 arehereinafter referred to as “audio streams #1 or “primary audio streams”.The audio streams represented by number_of_audio_stream2_entries decodedby the second audio decoder 75-2 of the playback apparatus 20 or 401 arehereinafter referred to as “audio streams #2” or “secondary audiostreams”. The audio streams #1 are played back preferentially over theaudio streams #2.

The number_of_PG_txtST_stream_entries indicates the number of streamsprovided with PG_txtST_stream_id entered in the STN_table( ). In theSTN_table( ) shown in FIG. 14, streams (presentation graphics streams(PG)) in which bitmap subtitles, such as DVD sub-pictures, arerun-length coded, and text subtitle files (txtST) are entered. ThePG_txtST_stream_id is information for identifying the subtitle streams,and PG_txtST_stream_number is the subtitle stream number (text subtitlestream number) that can be seen by the user when switching subtitles.

The number of IG stream entries indicates the number of streams providedwith IG_stream_id entered in STN_table( ). In STN_( ) shown in FIG. 14,interactive graphics streams are entered. IG_stream_id is informationfor identifying the interactive graphics streams. The IG_stream_numberis the graphics stream number that can be seen when switching graphics.

The syntax of stream_entry( ) is discussed below with reference to FIG.15.

The length field is an 8-bit unsigned integer indicating the number ofbytes from immediately after the length field to the end ofstream_entry( ).

The type is an 8-bit field indicating the type of information requiredfor uniquely specifying the stream provided with the above-describedstream number.

If type=1, a 16-bit packet ID (PID) is designated for specifying oneelementary stream from a plurality of elementary streams multiplexedinto the main clip referred to by the play item. Theref_to_stream_PID_of_mainClip indicates this PID. That is, if type=1,the stream can be determined only by specifying the PID in the main clipAV stream file.

If type=2, to specify one elementary stream from a plurality ofelementary streams multiplexed into one clip referred to by the sub-pathincluding a plurality of clips, SubPath_id of the sub-path, Clip_id, andpacket ID (PID) are designated. The ref_to_SubPath_id indicates theSubPath_id, the ref_to_SubClip_entry_id indicates the Clip_id, and theref_to_stream_PID_of_SubClip indicates the PID. This field is used whena plurality of clips are referred to by a sub-play item and when aplurality of elementary streams are referred to by each clip.

In this manner, when a play item and at least one sub-path played backin association with the play item are provided, type (type 1 and type 2)can be used for specifying one elementary stream from the clip referredto by the play item and clips referred to by at least one sub-path.Type=1 indicates the main clip referred to by the main path and type=2indicates a sub-clip referred to by a sub-path.

Referring back to a description of STN_table( ) in FIG. 14, in the FORloop of the video stream ID (video_stream_id), video_stream_id isassigned from 0 to a video elementary stream specified for eachstream_entry( ). Instead of the video stream ID (video_stream_id), thevideo stream number (video_stream_number) is used, in which case, thenumber is assigned from 1. That is, the number obtained by adding one tovideo_stream_id is the video_stream_number. The number is assigned from1 since video_stream_number is the video stream number that can be seenby the user when switching video.

Similarly, in the FOR loop of the audio stream ID (audio_stream_id),audio_stream_id is assigned from 0 to an audio elementary streamspecified for each stream_entry( ). As in the video stream, instead ofthe audio stream ID (audio_stream_id), the audio stream number(audio_stream_number) is used, in which case, the number is assignedfrom 1. That is, the number obtained by adding one to audio_stream id isthe audio_stream_number. The number is assigned from 1 sinceaudio_stream_number is the audio stream number that can be seen by theuser when switching sound.

Similarly, in the FOR loop of the audio stream ID2 (audio_stream_id2),audio_stream_id2 is assigned from 0 to an audio elementary streamspecified for each stream_entry( ). As in the video stream, instead ofthe audio stream ID2 (audio_stream_id2), the audio stream number 2(audio_stream_number2) is used, in which case, the number is assignedfrom 1. That is, the number obtained by adding one to audio_stream_id2is the audio_stream_number2. The number is assigned from 1 sinceaudio_stream_number2 is the audio stream number 2 that can be seen bythe user when switching sound.

That is, in the first STN_table( ) in FIG. 14, the audio streams #1represented by number_of_audio_stream_entries and the audio streams #2represented by number_of_audio_stream2_entries are defined. In otherwords, by using the first STN_table( ), the audio streams #1 and theaudio streams #2 can be entered so that the user can select two audiostreams to be played back simultaneously.

Similarly, in the FOR loop of the subtitle stream ID(PG_txtST_stream_id), PG_txtST_stream_id is assigned from 0 to a bitmapsubtitle or text subtitle elementary stream specified for eachstream_entry( ). As in the video stream, instead of the subtitle streamID (PG_txtST_stream_id), the subtitle stream number(PG_txtST_stream_number) is used, in which case, the number is assignedfrom 1. That is, the number obtained by adding one to PG_txtST_stream_idis the PG_txtST_stream_number. The number is assigned from 1 sincePG_txtST_stream_number is the bitmap subtitle or text subtitle streamnumber that can be seen by the user when switching subtitles.

Similarly, in the FOR loop of the graphics stream ID (IG_stream_id),IG_stream_id is assigned from 0 to an interactive graphics elementarystream specified for each stream_entry( ). As in the video stream,instead of the graphics stream ID (IG_stream_id), the graphics streamnumber (IG_stream_number) is used, in which case, the number is assignedfrom 1. That is, the number obtained by adding one to IG_stream_id isthe IG_stream_number. The number is assigned from 1 sinceIG_stream_number is the graphics stream number that can be seen by theuser when switching graphics.

The syntax of stream_attribute( ) is discussed below with reference toFIG. 16.

The length field is a 16-bit unsigned integer indicating the number ofbytes from the length field to the end of stream_attribute( ).

The stream_coding_type indicates the coding type of elementary stream,as shown in FIG. 17. The coding types of elementary streams includevideo codec formats, such as MPEG2 video stream, audio codec formats,such as HDMV LPCM audio, Dolby AC-3 audio, dts audio, Presentationgraphics stream, Interactive graphics stream, and Text subtitle stream.

The video_format indicates the video format of a video elementarystream, as shown in FIG. 18. The video formats of the video elementarystreams include 480i, 576i, 480p, 1080i, 720p, and 1080p.

The frame_rate indicates the frame rate of a video elementary stream, asshown in FIG. 19. The frame rates of the video elementary streamsinclude 24000/1001, 24, 25, 30000/1001, 50, and 60000/1001.

The aspect_ratio indicates the aspect ratio of a video elementarystream, as shown in FIG. 20. The aspect ratios of the video elementarystreams include 4:3 display aspect ratio and 16:9 display aspect ratio.

The audio_presentation_type indicates the presentation type of an audioelementary stream, as shown in FIG. 21. The presentation types of audioelementary streams include single mono channel, dual mono channel,stereo (2-channel), and multi-channel.

The sampling_frequency indicates the sampling frequency of an audioelementary stream, as shown in FIG. 22. The sampling frequencies of theaudio elementary streams include 48 kHz and 96 kHz.

The audio_language_code indicates the language code (for example,Japanese, Korean, or Chinese) of an audio elementary stream.

The PG_language_code indicates the language code (for example, Japanese,Korean, or Chinese) of a bitmap subtitle elementary stream.

The IG_language_indicates the language code (for example, Japanese,Korean, or Chinese) of an interactive graphics elementary stream.

The textST_language_code indicates the language code (for example,Japanese, Korean, or Chinese) of a text subtitle elementary stream.

The character_code indicates the character code of a text subtitleelementary stream, as shown in FIG. 23. The character codes of textsubtitle elementary streams include Unicode V1.1 (ISO 10646-1), ShiftJIS (Japanese), KSC 5601-1987 including KSC 5653 for Roman character(Korean), GB18030-2000 (Chinese), GB2312 (Chinese), and BIG5 (Chinese).

A specific example of the syntax of stream_attribute( ) shown in FIG. 16is described below with reference to FIGS. 16, and 17 through 23.

If the coding type (stream_coding_type in FIG. 16) of the elementarystream is the MPEG2 video stream (FIG. 17), stream_attribute( ) includesthe video format (FIG. 18), the frame rate (FIG. 19), and the aspectratio (FIG. 20) of the elementary stream.

If the coding type (stream_coding_type in FIG. 16) of the elementarystream is the HDMV LPCM audio, Dolby AC-3 audio, or dts audio (FIG. 17),stream_attribute( ) includes the audio presentation type (FIG. 21), thesampling frequency (FIG. 22), and the language code of the audioelementary stream.

If the coding type (stream_coding_type in FIG. 16) of the elementarystream is the Presentation graphics stream (FIG. 17), stream_attribute() includes the language code of the bitmap subtitle elementary stream.

If the coding type (stream_coding_type in FIG. 16) of the elementarystream is the Interactive graphics stream (FIG. 17), stream_attribute( )includes the language code of the interactive graphics elementarystream.

If the coding type (stream_coding_type in FIG. 16) of the elementarystream is the Text subtitle stream (FIG. 17), stream_attribute( )includes the character code (FIG. 23) and the language code of the textsubtitle elementary stream.

The attribute information is not restricted to the above-describedtypes.

In this manner, if a play item and at least one sub-path played back inassociation with the play item are provided, by referring to the clipreferred to by the play item and clips referred to by at least onesub-path, attribute information concerning an elementary streamspecified by stream_entry( ) can be defined by stream_attribute( ).

By checking the attribute information (stream_attribute( )), theplayback apparatus can determine whether it has a function of playingback the corresponding elementary stream. Also, by checking theattribute information, the playback apparatus can select the elementarystreams in accordance with the initial information concerning thelanguage set in the playback apparatus.

It is now assumed, for example, that the playback apparatus has afunction of playing back bitmap subtitle elementary streams without afunction of playing back text subtitle elementary streams. In this case,in response to an instruction to switch the languages from the user, theplayback apparatus sequentially selects only bitmap subtitle elementarystreams from the FOR loop of the subtitle stream ID (PG_txtST_stream_id)and plays back the selected elementary streams.

If the initial information concerning the language set in the playbackapparatus is Japanese, in response to an instruction to switch from mainaudio to secondary audio or to mix main audio with secondary audio fromthe user, the playback apparatus sequentially selects only audioelementary stream whose language code is Japanese from the FOR loop ofthe audio stream ID (audio_stream_id) prepared as secondary audio andplays back the selected elementary streams.

If AV video streams and AV audio streams (movie) referred to by a mainpath are played back, in response to an instruction to switch sound andto mix an audio stream (director's or performers' commentaries) referredto by a sub-path with an AV stream referred to by the main path from theuser, the playback apparatus mixes (superimposes) the second audiostream referred to by the sub-path with (on) the first audio streamreferred to by the main path, and plays back the mixed audio streamstogether with the video streams.

The STN_table( ) shown in FIGS. 14 and 15 shows that both the audiostream #1 and the audio stream #2 may be audio streams contained inclips referred to by a main path. Alternatively, one of the audio stream#1 and the audio stream #2 may be an audio stream contained in a clipreferred to by a main path, and the other audio stream may be an audiostream contained in a clip referred to by a sub-path. In this manner,two audio streams superimposed on main AV streams referred to by themain path may be selected and mixed.

As described above, by the provision of STN_table( ) in PlayItem( ), ifa play item and at least one sub-path played back in association withthe play item are provided, the user can select a stream to be playedback from the clip referred to by the play item and clips referred to byat least one sub-path when switching sound or subtitles. Thus,interactive operations can be performed for streams or data filesdifferent from an AV stream to be played back.

Since one playlist includes a plurality of sub-paths and each sub-pathrefers to a sub-play item, AV streams having high extensibility and highflexibility are implemented. That is, sub-play items can be addedafterwards to the content played back by using the playlist. Forexample, if a playlist including a clip AV stream file referred to bythe main path is replaced by a playlist including the clip AV streamfile and a new sub-path, the user can select based on the new playlist,not only from the clip AV stream file referred to by the main path, butalso from the clip AV stream file referred to by the sub-path. Thus, theAV streams have high extensibility.

By the provision of the STN_table( ) in PlayItem( ), the audio stream #1decoded by a first audio decoder 75-1 of the playback apparatus 20 inFIG. 25 or the playback apparatus 401 in FIG. 49 can be mixed with theaudio stream #2 decoded by a second audio decoder 75-2 of the playbackapparatus 20 or 401. For example, if PlayItem( ) and at least onesub-path played back in association with PlayItem( ) are provided, anaudio stream contained in the clip referred to by the play item is setto be the audio stream #1, and an audio stream contained in the clipreferred to by the sub-path is set to be the audio stream #2, and then,the audio stream #1 and the audio stream #2 are mixed and played back.Alternatively, two audio streams contained in the main clip referred toby the play item may be set as the audio stream #1 and the audio stream#2 and are mixed and played back. With this configuration, an audiostream (for example, director's commentaries) different from the mainaudio stream can be superimposed on the main audio stream. Additionally,two audio streams #1 and #2 superimposed on the main clip AV stream canbe superimposed and played back.

A specific example is given with reference to FIG. 24. FIG. 24illustrates an example of the stream number table indicating soundnumbers and subtitle numbers provided to users.

In FIG. 24, the sound numbers are referred to as “A_SN” and A_SN2 andthe subtitle numbers are referred to as “S SN”. In FIG. 24, each of theplurality of audio streams #1 entered in STN_table( ) of the play itemforming the main path of the playlist (audio stream entered asaudio_stream_id) is provided with A_SN, and each of the plurality ofaudio streams #2 entered in STN_table( ) of the play item forming themain path of the playlist (audio stream entered as audio_stream_id2) isprovided with A_SN2.

That is, audio 2 is assigned to A_SN=1, audio 1 is assigned to A_SN=2,and audio 3 is assigned to A_SN=3. Audio 4 is assigned to A_SN2=1, andaudio 5 is assigned to A_SN2=2. The user selects an audio stream #1 tobe played back from among the audio streams assigned to A_SN, andselects an audio stream #2 to be mixed with the selected audio stream #1from among the audio streams assigned to A_SN2. For example, the userselects audio 1 assigned to A_SN=2 and audio 5 assigned to A_SN2=2.

More specifically, if the user gives an instruction to switch audiostreams while audio 2 assigned to A_SN=1 is being selected, audio 2 isswitched to audio 1 assigned to A_SN=2. If the user further gives aninstruction to switch audio streams, audio 1 is switched to audio 3assigned to A_SN=3. If the user further gives an instruction to switchaudio streams, audio 3 is switched back to audio 2 assigned to A_SN=1.Also, if the user gives an instruction to switch audio streams whileaudio 4 assigned to A_SN2=1 is being selected, audio 4 is switched toaudio 5 assigned to A_SN2=2. If the user further gives an instruction toswitch audio streams, audio 5 is switched back to audio 4 assigned toA_SN2=1. In this manner, A_SN for selecting audio stream #1 and A_SN2for selecting audio stream #2 are independent of each other. That is,the user selects one audio stream from A_SN=1 through A_SN=3 and selectsone audio stream from A_SN2=1 through A_SN2=2.

Each of a plurality of sub-picture streams of the main AV streamreferred to by the main path is provided with S_SN. More specifically,sub-picture 3 is assigned to S_SN=1, sub-picture 1 is assigned toS_SN=2, and sub-picture 2 is assigned to S_SN=3.

In this case, as A_SN, A_SN2, or S_SN indicates a smaller number, thecorresponding audio stream or sub-picture stream is provided to the userwith higher priority. Streams provided by A_SN has higher priority overstreams provided by A_SN2. That is, A_SN=1 is an audio stream playedback as a default, and S_SN=1 is a sub-picture stream played back as adefault.

More specifically, sound played back based on the initial informationconcerning the language set in the playback apparatus is audio 2 (FIG.24), which is A_SN=1, and sound played back after being switched fromaudio 2 is audio 1, which is A_SN=2 (FIG. 24).

To provide such a stream number table, in STN_table( ) (FIG. 14) inPlayItem( ) referred to by PlayList( ), for the entry of audio stream#1, audio_stream_id=0 (A_SN=1) is assigned to audio 2, audio_stream_id=1(A_SN=2) is assigned to audio 1, audio_stream_id=2 (A_SN=3) is assignedto audio 3. Then, in STN_table( ) (FIG. 14), for the entry of audiostream #2, audio_stream_id2=0 (A_SN2=1) is assigned to audio 4, andaudio_stream_id2=1 (A_SN2=2) is assigned to audio 5.

That is, by separately defining two types of audio streams (audio stream#1 and audio stream #2) to be played back, the user can select two audiostreams as desired from the defined streams. Accordingly, theflexibility in selecting audio streams becomes high. For example, theuser can select a combination of audio 2 and audio 4 (A_SN=1 andA_SN2=1) or a combination of audio 2 and audio 5 (A_SN=1 and A_SN2=2).

As described above, in stream_entry( ) (FIG. 15) of the STN_table( )(FIG. 14) in PlayItem( ), two audio streams can be entered so that twoaudio streams can be mixed and played back. That is, two streams of thesame type (in this case, audio streams) can be selected from streams ofdifferent types so that they can be mixed (superimposed or combined) andplayed back simultaneously. The user can give an instruction to mix andplay back the streams.

A playback apparatus according to an embodiment of the present inventionis discussed below with reference to the block diagram of FIG. 25. Theplayback apparatus 20 shown in FIG. 25 plays back a playlist includingthe above-described main path and sub-path.

The playback apparatus 20 includes a storage drive 31, a switch 32, anAV decoder 33, and a controller 34.

The controller 34 controls the storage drive 31 to read a playlist fileand to read AV streams or AV data from a recording medium, such as anHDD, Blu-ray disc™, or a DVD, based on information stored in theplaylist file. The user instructs the controller 34 to switch sound orsubtitles by using a user interface. Initial information concerning thelanguage set in the playback apparatus 20 is supplied to the controller34 from a storage unit (not shown).

The playlist file includes, not only information concerning a main pathand information concerning sub-paths, but also STN_table( ). Thecontroller 34 reads a main clip AV stream file referred to by a playitem contained in the playlist file, a sub-clip AV stream file referredto by a sub-play item, and text subtitle data referred to by a sub-playitem via the storage drive 31. In this case, the main clip AV streamreferred to by the play item and the sub-clip AV stream referred to bythe sub-play item may be recorded on different recording media. Forexample, the main clip AV stream may be recorded on the recordingmedium, and the corresponding sub-clip AV stream may be supplied via anetwork (not shown) and stored in an HDD. The controller 34 controls theplayback apparatus 20 to select and play back elementary streams inaccordance with the playback function of the playback apparatus 20 or toselect and play back elementary streams in accordance with the initialinformation concerning the language set in the playback apparatus 20.Generally, since a stream referred to by a play item includes a videostream, a clip including a stream referred to by the play item (mainpath) is referred to as a “main clip”. Streams other than the main clipare referred to as “sub-clips”. Sub-clips are streams referred to bysub-paths, and a clip including at least one stream of a video streamsubstituting a video stream referred to by a play item, a video streamcombined with the video stream referred to by the play item, an audiostream without a video stream, an IG stream, and a PG stream.

The AV decoder 33 includes buffers 51 through 54, PID filters 55 and 56,switches 57 through 59, a background decoder 71, s video decoder 72, apresentation graphics decoder 73, an interactive graphics decoder 74,the first audio decoder 75-1, the second audio decoder 75-2, a textsubtitle (ST) composition 76, a switch 77, a background plane generator91, a video plane generator 92, a presentation graphics plane generator93, an interactive graphics plane generator 94, a buffer 95, a videodata processor 96, and mixing processors 97 and 98. The first and secondaudio decoders 75-1 and 75-2 decode audio stream #1 and audio stream #2,respectively. More specifically, in STN_table( ) shown in FIG. 14, thedecoder that decodes the audio stream represented by audio_stream_id isthe first audio decoder 75-1, and the decoder that decodes the audiostream represented by audio_stream_id2 is the second audio decoder 75-2.

As described above, the playback apparatus 20 includes two audiodecoders, i.e., the first audio decoder 75-1 and the second audiodecoder 75-2, for decoding two audio streams. Hereinafter, the first andsecond audio decoders 75-1 and 75-2 are simply referred to as the “audiodecoder 75” unless they have to be distinguished from each other.

File data read by the controller 34 is demodulated by a demodulator, andthe demodulated multiplexed streams are then subjected to errorcorrection by an error-correcting code (ECC) decoder. The switch 32 thendivides the multiplexed streams according to the stream types andsupplies the divided streams to the corresponding buffers 51 through 54under the control of the controller 34. More specifically, under thecontrol of the controller 34, the switch 32 supplies background imagedata to the buffer 51, main clip AV stream data to the buffer 52,sub-clip AV stream data to the buffer 53, and text-ST data to the buffer54. Then, the buffers 51 through 54 buffer the background image data,main clip AV stream data, sub-clip AV stream data, and text-ST data,respectively, therein.

The main clip AV stream is a stream (for example, a transport stream) inwhich at least one stream of video, audio, bitmap subtitle (presentationgraphics), and interactive graphics streams is multiplexed together witha video stream. The sub-clip AV stream is a stream in which at least onestream of audio, bitmap subtitle (presentation graphics), andinteractive graphics streams is multiplexed. The text subtitle data filemay be a multiplexed stream, such as a transport stream, but this is notessential.

When reading the main clip AV stream, the sub-clip AV stream, and thetext subtitle data from the storage drive 31 or the recording medium,they can be alternately read in a time-division manner. Alternatively,the sub-clip AV stream or the text subtitle data may be entirelypreloaded to the buffer 53 or 54, respectively.

The playback apparatus 20 reads those data from the recording medium 11via the storage drive 31 to play back video, bitmap subtitle,interactive graphics, and audio.

More specifically, stream data read out from the buffer 52, which servesas the clip AV stream read buffer, is output to the PID filter 55 at apredetermined time. The PID filter 55 allocates streams contained in themain clip AV stream file to the corresponding elementary stream decodersaccording to the PIDs. More specifically, the PID filter 55 suppliesvideo streams to the video decoder 72, presentation graphics streams tothe switch 57, which supplies the graphics streams to the presentationgraphics decoder 73, interactive graphics streams to the switch 58,which supplies the graphics streams to the interactive graphics decoder74, and audio streams to the switch 59, which supplies the audio streamsto the first audio decoder 75-1.

The presentation graphics streams are, for example, bitmap subtitledata, and the interactive graphics streams are, for example, textsubtitle data.

Stream data read out from the buffer 53, which serves as the sub-clip AVstream read buffer, is output to the PID filter 56 at a predeterminedtime. The PID filter 56 allocates streams contained in the sub-clip AVstream to the corresponding elementary stream decoders according to thePIDs. More specifically, the PID filter 56 supplies presentationgraphics streams to the switch 57, which supplies the graphics streamsto the presentation graphics decoder 73, interactive graphics streams tothe switch 58, which supplies the graphics streams to the interactivegraphics decoder 74, and sub-clip audio streams to the switch 59, whichsupplies the audio streams to the first audio decoder 75-1 and thesecond audio decoder 75-2.

Data read out from the buffer 51, which serves as the background imagedata buffer, is supplied to the background decoder 71 at a predeterminedtime. The background decoder 71 decodes the background image data, andthen supplies the decoded data to the background plane generator 91.

The video streams allocated by the PID filter 55 are supplied to thevideo decoder 72. The video decoder 72 decodes the video streams andsupplies the decoded video streams to the video plane generator 92.

The switch 57 selects one of the presentation graphics streams containedin the main clip AV stream supplied from the PID filter 55 and thepresentation graphics streams contained in the sub-clip AV streamsupplied from the PID filter 56, and supplies the selected presentationgraphics streams to the presentation graphics decoder 73. Thepresentation graphics decoder 73 decodes the presentation graphicsstreams and supplies them to the switch 77, which further supplies themto the presentation graphics plane generator 93.

The switch 58 selects one of the interactive graphics streams containedin the main clip AV stream supplied from the PID filter 55 and theinteractive graphics streams contained in the sub-clip AV streamsupplied from the PID filter 56, and supplies the selected interactivegraphics streams to the interactive graphics stream decoder 74. That is,the interactive graphics streams simultaneously input into theinteractive graphics decoder 74 are streams separated from the main clipAV stream file or the sub-clip AV stream file. The interactive graphicsdecoder 74 decodes the interactive graphics streams, and supplies thedecoded streams to the interactive graphics plane generator 94.

The switch 59 selects one of the audio streams contained in the mainclip AV stream supplied from the PID filter 55 and the audio streamscontained in the sub-clip AV stream supplied from the PID filter 56 andsupplies the selected audio streams to the first audio decoder 75-1 orthe second audio decoder 75-2. The audio streams simultaneously inputinto the first audio decoder 75-1 are streams separated from the mainclip or the sub-clip. The audio streams simultaneously input into thesecond audio decoder 75-2 are streams separated from the sub-clip AVstream file. If the main clip AV stream includes the audio streams #1and the audio streams #2, the PID filter 161 filters the audio streams#1 and the audio streams #2 according to the PIDs of the audio streams,and supplies them to the switch 59.

The switch 59 selects the audio streams #1 supplied from the PID filter55 to the first audio decoder 75-1 and the audio streams #2 suppliedfrom the PID filter 55 to the second audio decoder 75-2.

The first audio decoder 75-1 decodes the audio streams and supplies thedecoded audio streams to the mixing processor 98. The second audiodecoder 75-2 decodes the audio streams #2 and supplies the decoded audiostreams to the mixing processor 98.

If an instruction to superimpose the audio stream #1 on the audio stream#2 and play back the superimposed stream is given (if two audio streamsare selected), the specified audio stream #1 decoded by the first audiodecoder 75-1 and the specified audio stream #2 decoded by the secondaudio decoder 75-2 are supplied to the mixing processor 98.

The mixing processor 98 mixes (superimposes) the audio data from thefirst audio decoder 75-1 with the audio data from the second audiodecoder 75-2, and supplies the resulting data to the mixing processor97. In this embodiment, mixing (superimposing) of the audio data outputfrom the first audio decoder 75-1 and the audio data output from thesecond audio decoder 75-2 is also referred to as “combining”. That is,to combine two audio data is to mix two audio data.

Sound data selected by the switch 32 is supplied to the buffer 95 and isbuffered therein. The buffer 95 supplies the sound data to the mixingprocessor 97 at a predetermined time. The sound data is, for example,effect sound that can be selected from a menu. The mixing processor 97mixes (superimposes or combines) the audio data mixed by the mixingprocessor 98 (audio data obtained by mixing the audio data output fromthe first audio decoder 75-1 with the audio data output from the secondaudio decoder 75-2) with the sound data supplied from the buffer 95, andoutputs the resulting data as an audio signal.

Data read from the buffer 54, which serves as the text subtitle readbuffer, is output to the text subtitle composition 76 at a predeterminedtime. The text subtitle composition 76 decodes the text-ST data andsupplies the decoded data to the switch 77.

The switch 77 selects one of the presentation graphics streams decodedby the presentation graphics decoder 73 and the text subtitle datadecoded by the text subtitle composition 76, and supplies the selecteddata to the presentation graphics plane generator 93. That is, subtitleimages simultaneously supplied to the presentation graphics planegenerator 93 are those output from the presentation graphics decoder 73or from the text subtitle composition 76. Presentation graphics streamssimultaneously input into the presentation graphics decoder 73 arestreams separated from the main clip AV stream or from the sub-clip AVstream (selected by the switch 57). Accordingly, the subtitle imagessimultaneously input into the presentation graphics plane generator 93are presentation graphics streams from the main clip AV stream file,presentation graphics streams from a sub-clip AV stream file, or textsubtitle data.

The background plane generator 91 generates a background plane, whichserves as, for example, a wallpaper image when a video image isdisplayed by reducing the size thereof, on the basis of the backgroundimage data supplied from the background decoder 71, and supplies thegenerated background plane to the video data processor 96. The videoplane generator 92 generates a video plane based on the video datasupplied from the video decoder 72, and supplies the generated videoplane to the video data processor 96. The presentation graphics planegenerator 93 generates a presentation graphics plane, which serves as,for example, a rendering image, on the basis of the data (presentationgraphics streams or text subtitle data) selected by the switch 77, andsupplies the generated presentation graphics plane to the video dataprocessor 96. The interactive graphics plane generator 94 generates aninteractive graphics plane based on the interactive graphics stream datasupplied from the interactive graphics decoder 74, and supplies thegenerated interactive graphics plane to the video data processor 96.

The video data processor 96 combines the background plane from thebackground plane generator 91, the video plane from the video planegenerator 92, the presentation graphics plane from the presentationgraphics plane generator 93, and the interactive graphics plane from theinteractive graphics plane generator 94, and outputs the combined planeas a video signal. The mixing processor 97 mixes (superimposes orcombines) the audio data supplied from the mixing processor 98 and thesound data supplied from the buffer 95, and outputs the resulting dataas an audio signal.

The switches 57 through 59 and the switch 77 select data according tothe selection by the user via a user interface or depending on the typeof file containing target data. For example, if audio streams arecontained only in sub-clip AV stream files, the switch 59 changes theselection to the PID filter 56, which supplies data contained in thesub-clip AV stream files.

The playback processing performed by the playback apparatus 20 shown inFIG. 25 is described below with reference to the flowcharts in FIGS. 26through 28. This processing is started when an instruction to play backa predetermined AV stream is given from a user via a user interface.

In step S11, the controller 34 reads a playlist file, such as that shownin FIG. 9, recorded on a recording medium or an HDD (not shown) via thestorage drive 31.

In step S12, the controller 34 reads a main clip AV stream, a sub-clipAV stream, and text subtitle data (text-ST data). More specifically, thecontroller 34 reads the corresponding main clip AV stream from the mainclip based on the play item contained in the playlist shown in FIG. 9,and also reads a sub-clip AV stream and text subtitle data based on asub-play item shown in FIGS. 10 through 12, which is referred to by asub-path contained in the playlist.

In step S13, the controller 34 controls the switch 32 to supply the readdata (main clip AV stream, sub-clip AV stream, and text subtitle data)to the corresponding buffers 51 through 54. More specifically, thecontroller 34 controls the switch 32 to supply the background image datato the buffer 51, the main clip AV stream data to the buffer 52, thesub-clip AV stream data to the buffer 53, and the text subtitle data tothe buffer 54.

In step S14, the switch 32 supplies the corresponding data as describedabove under the control of the controller 34.

In step S15, the buffers 51 through 54 buffer the supplied data therein.More specifically, the buffer 51 buffers the background image data, thebuffer 52 buffers the main clip AV stream data, the buffer 53 buffersthe sub-clip AV stream data, and the buffer 54 buffers the text subtitledata.

In step S16, the buffer 51 outputs the background image data to thebackground decoder 71.

In step S17, the buffer 52 outputs the stream data of the main clip AVstream to the PID filter 55.

In step S18, the PID filter 55 allocates the elementary streams to thecorresponding elementary stream decoders based on the PIDs attached tothe transport stream packets forming the main clip AV stream file. Morespecifically, the PID filter 55 supplies video streams to the videodecoder 72, presentation graphics streams to the switch 57, whichsupplies the streams to the presentation graphics decoder 73,interactive graphics streams to the switch 58, which supplies thestreams to the interactive graphics decoder 74, and audio streams to theswitch 59, which supplies the streams to the first audio decoder 75-1.As discussed above, the video streams, presentation graphics streams,interactive graphics streams, and audio streams are provided withdifferent PIDs.

In step S19, the buffer 53 outputs the stream data of the sub-clip AVstream to the PID filter 56.

In step S20, the PID filter 56 allocates the elementary streams to thecorresponding decoders based on the PIDs. More specifically, the PIDfilter 56 supplies presentation graphics streams to the switch 57, whichsupplies the streams to the presentation graphics decoder 73,interactive graphics streams to the switch 58, which supplies thestreams to the interactive graphics decoder 74, and audio streams to theswitch 59, which supplies the streams to the first audio decoder 75-1 orthe second audio decoder 75-2.

In step S21, the switches 57 through 59 select one of the main clip AVstream and the sub-clip AV stream under the control of the controller 34via a user interface. More specifically, the switch 57 selectspresentation graphics streams of the main clip AV stream or those of thesub-clip AV stream supplied from the PID filter 55, and supplies theselected streams to the presentation graphics decoder 73. The switch 58selects interactive graphics streams of the main clip AV stream or thoseof the sub-clip AV stream supplied from the PID filter 55, and suppliesthe selected streams to the interactive graphics decoder 74. The switch59 selects audio streams of the main clip AV stream or those of thesub-clip AV stream supplied from the PID filter 55, and supplies theselected streams to the first audio decoder 75-1. If an instruction toswitch sound is given from the user, the switch 59 supplies audiostreams of a sub-clip AV stream to the second audio decoder 75-2.However, an explanation thereof is not given here since switching soundis not considered in this processing.

In step S22, the buffer 54 outputs text subtitle data to the textsubtitle composition 76.

In step S23, the background decoder 71 decodes background image data andsupplies the decoded data to the background plane generator 91.

In step S24, the video decoder 72 decodes the video streams and suppliesthe decoded streams to the video plane generator 92.

In step S25, the presentation graphics decoder 73 decodes thepresentation graphics streams selected by the switch 57, and outputs thedecoded streams to the switch 77.

In step S26, the interactive graphics decoder 74 decodes the interactivegraphics streams selected by the switch 58, and outputs the decodedstreams to the interactive graphics plane generator 94.

In step S27, the first audio decoder 75-1 decodes the audio stream(audio stream #1) selected by the switch 59 and outputs the decoded datato the mixing processor 98. In the playback processing shown in FIGS. 26through 28 when an instruction to switch sound is not given from theuser, audio data is not output from the second audio decoder 75-2.Accordingly, the mixing processor 98 directly supplies the audio dataoutput from the first audio decoder 75-1 to the mixing processor 97.

In step S28, the text subtitle composition 76 decodes text subtitle dataand outputs the decoded data to the switch 77.

In step S29, the switch 77 selects data from the presentation graphicsdecoder 73 or the text subtitle composition 76. More specifically, theswitch 77 selects the presentation graphics streams decoded by thepresentation graphics decoder 73 or the text subtitle data from the textsubtitle composition 76, and supplies the selected data to thepresentation graphics plane generator 93.

In step S30, the background plane generator 91 generates a backgroundplane based on the background image data supplied from the backgrounddecoder 71.

In step S31, the video plane generator 92 generates a video plane basedon the video data supplied from the video decoder 72.

In step S32, the presentation graphics plane generator 93 generates apresentation graphics plane based on the data selected by the switch 77in step S29 and supplied from the presentation graphics decoder 73 orthe text subtitle composition 76.

In step S33, the interactive graphics plane generator 94 generates aninteractive graphics plane based on the interactive graphics stream datasupplied from the interactive graphics decoder 74.

In step S34, the buffer 95 buffers the sound data selected in step S14and supplies it to the mixing processor 97 at a predetermined time.

In step S35, the video data processor 96 combines the planes and outputsthe combined data. More specifically, the video data processor 96combines the data from the background plane generator 91, the videoplane generator 92, the presentation graphics plane generator 93, andthe interactive graphics plane generator 94, and outputs the combineddata as video data.

In step S36, the mixing processor 97 mixes (combines) the audio dataoutput from the mixing processor 98 with the sound data, and outputs theresulting data. The processing is then completed.

According to the processing shown in FIGS. 26 through 28, by referringto the main clip AV stream referred to by the main path included in theplaylist, a sub-clip AV stream referred to by the corresponding sub-pathincluded in the playlist, and the text subtitle data, the correspondingdata is played back. By providing the main path and the sub-path in theplaylist, a clip AV stream, which is different from the main clip AVstream specified by the main path, can be specified by the sub-path.Thus, data of a sub-clip AV stream file, which is different from themain clip specified by the play item of the main path, can be playedback together with (in synchronization with) the data of the main clipAV stream file contained in the main clip.

In FIGS. 26 through 28, the order of steps S16 and S17 may be reversedor steps S16 and S17 may be executed in parallel. Similarly, the orderof steps S18 and S20 may be reversed or steps S18 and S20 may beexecuted in parallel. The order of steps S23 through S28 may be reversedor steps S23 through S28 may be executed in parallel. The order of stepsS30 through S33 may be reversed or steps S30 through S33 may be executedin parallel. The order of steps S35 and S36 may be reversed or steps S35and S36 may be executed in parallel. That is, in FIG. 25, the elementsdisposed vertically on the same layer, i.e., the processing jobs of thebuffers 51 through 54, those of the switches 57 through 59, those of thedecoders 71 through 76, those of the plane generators 91 through 94, andthose of the video data processor 96 and the mixing processor 97 may beexecuted in parallel, and the order thereof is not particularlyrestricted.

Processing performed by the playback apparatus 20 when an instruction toswitch sound is given is now described with reference to the flowchartin FIGS. 29 and 30. Reference is first given to the flowchart in FIG. 29to describe processing when an instruction to switch sound for audiostreams #1 is given. Processing when an instruction to switch sound foraudio streams #2 is given is discussed below with reference to FIG. 30.The processing shown in FIGS. 29 and 30 is executed while performing,for example, the playback processing shown in FIGS. 26 through 28.

In step S51, the controller 34 obtains an order list of audio streamnumbers (may be audio stream IDs). More specifically, the controller 34refers to STN_table( ) of PlayItem( ) discussed with reference to FIG.13 to obtain the order list of audio stream numbers (IDs) entered inSTN_table( ) discussed with reference to FIG. 14. This step is executedwhen the playback processing shown in FIGS. 26 through 28 is started.

In response to an instruction to switch sound for audio streams #1 givenfrom the user via a user interface, in step S52, the controller 34receives the instruction. In this case, the controller 34 may control adisplay device (not shown) to display a stream number table, such asthat shown in FIG. 24, on the display device. Since the processing shownin FIG. 29 is to perform sound switching for the audio streams #1, theuser gives an instruction to switch sound of A_SN=1, A_SN=2, or A_SN=3,and more specifically, to switch from audio 2 (A_SN=1) to audio 1(A_SN=2). The controller 34 receives an instruction to switch from audio2 to audio 1 from the user. In FIG. 29, step S51 has been executed, andin response to an instruction to switch sound for the audio stream #1from the user, step S52 is executed.

In step S53, the controller 34 obtains the audio stream numbersubsequent to the audio stream number which is currently played back.For example, if the audio stream file corresponding to audio 2 (A_SN=1)shown in FIG. 24 is currently played back in step S52, the subsequentaudio stream is audio 1 (A_SN=2). Accordingly, the controller 34 obtainsthe audio stream number corresponding to audio 1.

In step S54, the controller 34 determines whether the playback apparatus20 has a function of playing back the audio stream (audio stream #1)associated with the obtained number. More specifically, the controller34 makes this determination based on the information indicated instream_attribute( ) shown in FIG. 16. For example, if type=1 instream_entry( ) in FIG. 15, the controller 34 determines whether thefunction of playing back the audio stream of the main clip AV streamassociated with the obtained number is provided. Since the audio streamassociated with the obtained number are the audio stream #1 decoded bythe first audio decoder 75-1, it is determined whether the audio decoder75-1 can decode the audio stream #1.

If it is determined in step S54 that the function of playing back theaudio stream associated with the obtained number is not provided, theprocess proceeds to step S55 in which the controller 34 obtains thestream number subsequent to the current stream number. That is, thecurrent stream number is skipped and is not played back. Then, afterstep S55, the process returns to step S54. That is, the processing isrepeated until the controller 34 obtains an audio stream (audio stream#1) number that can be played back by the playback apparatus 20.

If it is determined in step S54 that the function of playing back theaudio stream associated with the obtained number is provided, theprocess proceeds to step S56. In step S56, the controller 34 checks,based on the type shown in FIG. 15, the audio streams of the main clipAV stream contained in the main clip associated with the obtained number(type=1) and the audio streams of the sub-clip AV stream file containedin the sub clip associated with the obtained number (type=2). If type=1in stream_entry( ) in FIG. 15, the controller 34 can determine that theaudio stream associated with the obtained number is contained in themain clip. If type=2 in stream_entry( ) in FIG. 15, the controller 34can determine that the audio stream associated with the obtained numberis contained in the sub-clip.

In step S57, the controller 34 specifies a desired audio stream. Morespecifically, the controller 34 specifies a desired audio streamcontained in the main clip associated with the obtained number or thesub-clip associated with the obtained number. If it is determined instep S54 that the audio stream associated with the obtain number iscontained in the main clip, the controller 34 specifies thepredetermined audio stream contained in the main clip based oninformation (ref_to_stream_PID_of_mainClip) entered in stream_entry( )as type=1. If it is determined in step S54 that the audio streamassociated with the obtained number is contained in a sub-clip, thecontroller 34 specifies the predetermined audio stream contained in thesub-clip based on information (ref_to_SubPath_id,ref_to_SubPath_entry_id, and ref_to_stream_PID_of_SubClip) entered instream_entry( ) as type=2. The specified audio stream serves as theaudio stream #1 decoded by the first audio decoder 75-1.

In step S58, the controller 34 instructs the storage drive 31 to readthe clip AV stream (main clip AV stream or sub-clip AV stream)corresponding to the clip into which the desired audio stream ismultiplexed. In response to this instruction, the storage drive 31 readsthe target clip AV stream. More specifically, the controller 34instructs the storage drive 31 to read the clip AV stream specified instep S57.

In step S59, the controller 34 instructs the AV decoder 33 to play backthe audio stream from the read clip AV stream. More specifically, thecontroller 34 instructs the audio decoder 75-1 to decode the desiredaudio stream (i.e., audio stream #1) contained in the read clip AVstream.

In step S60, the AV decoder 33 decodes the audio stream (audio stream#1) and outputs it. More specifically, the audio decoder 75-1 of the AVdecoder 33 decodes the audio stream #1 (target audio stream in step S58)and outputs the decoded stream to the mixing processor 98. If the audiostream #2 is decoded by the second audio decoder 75-2 in the processingshown in FIG. 30, which is described below, the mixing processor 98mixes the audio stream #1 with the audio stream #2, and supplies themixed stream to the mixing processor 97. If the audio stream #2 is notdecoded by the second audio decoder 75-2 in the processing shown in FIG.30, the mixing processor 98 directly supplies the audio stream #1 to themixing processor 97. The mixing processor 97 then mixes the suppliedaudio data from the mixing processor 98 with the sound data output fromthe buffer 95, and outputs the resulting data as an audio signal.Details of step S60 are given below with reference to the flowchart inFIG. 31.

The processing performed in response to an instruction to perform soundswitching for the audio stream #2 is described below with reference tothe flowchart in FIG. 30. The playback apparatus 20 executes thisprocessing while performing the playback processing shown in FIGS. 26through 28. Generally, when the audio stream #2 is played back, theaudio stream #1 is also played back. Accordingly, the processing shownin FIG. 30 is executed in parallel with the playback processing for theaudio stream #1 shown in FIG. 29, and when the audio stream #2 is notselected by the user, only the playback processing for the audio stream#1 shown in FIG. 29 is performed without performing the processing shownin FIG. 30.

In step S71, the controller 34 obtains an order list of audio streamnumbers (may be audio stream IDs). More specifically, the controller 34refers to STN_table( ) of PlayItem( ) discussed with reference to FIG.13 to obtain the order list of audio stream numbers (IDs) entered inSTN_table( ) discussed with reference to FIG. 14. This step is executedwhen the playback processing shown in FIGS. 26 through 28 is started.

In response to an instruction to switch sound for audio streams #2 givenfrom the user via a user interface, in step S72, the controller 34receives the instruction. In this case, the controller 34 may control adisplay device (not shown) to display a stream number table, such asthat shown in FIG. 24, on the display device. Since the processing shownin FIG. 30 is to perform sound switching for the audio streams #2, theuser gives an instruction to switch sound between A_SN2=1 and A_SN=2,and more specifically, to switch from audio 4 (A_SN2=1) to audio 5(A_SN2=2). The controller 34 receives an instruction to switch fromaudio 4 to audio 5 from the user. In FIG. 30, step S71 has beenexecuted, and in response to an instruction to switch sound for theaudio streams #2 from the user, step S72 is executed.

In step S73, the controller 34 obtains the audio stream numbersubsequent to the audio stream number which is currently played back.For example, if the audio stream file represented by SubClip_entry_id=0shown in FIG. 8 is currently played back in step S72, the subsequentaudio stream represented by the subsequent SubClip_entry_id=1 isobtained. For example, if the audio stream file corresponding to audio 4(A_SN2=1) shown in FIG. 24 is currently played back in step S72, thesubsequent audio stream is audio 5 (A_SN2=2). Accordingly, thecontroller 34 obtains the audio stream number corresponding to audio 5.

In step S74, the controller 34 determines whether the playback apparatus20 has a function of playing back the audio stream (audio stream #2)associated with the obtained number. More specifically, the controller34 makes this determination based on the information indicated instream_attribute( ) shown in FIG. 16. For example, if type=1 instream_entry( ) in FIG. 15, the controller 34 determines whether thefunction of playing back the audio stream of the main clip AV streamassociated with the obtained number is provided. Since the audio streamassociated with the obtained number are the audio stream #2 decoded bythe first audio decoder 75-2, it is determined whether the audio decoder75-2 can decode the audio stream #2.

This processing may be omitted if the audio streams #1 decoded by thefirst audio decoder 75-1 have higher extensibility (as in multi-streams)than the audio streams #2 decoded by the second audio decoder 75-2. Forexample, if the first audio decoder 75-1 has higher performance than thesecond audio decoder 75-2 (if, for example, the audio streams #1 arenormal movie sound and the audio streams #2 are director's commentarieson that movie), it is highly likely that a certain restriction isimposed on the audio streams #2 decoded by the second audio decoder75-2. Accordingly, the possibility of streams that cannot be decoded bythe second audio decoder 75-2 being set as the audio streams #2 is low.

If it is determined in step S74 that the function of playing back theaudio stream associated with the obtained number is not provided, theprocess proceeds to step S75 in which the controller 34 obtains thestream number subsequent to the current stream number. That is, thecurrent stream number is skipped and is not played back. Then, afterstep S75, the process returns to step S74. That is, the processing isrepeated until the controller 34 obtains an audio stream (audio stream#2) number that can be played back by the playback apparatus 20.

If it is determined in step S74 that the function of playing back theaudio stream associated with the obtained number is provided, theprocess proceeds to step S76. In step S76, the controller 34 checks,based on the type shown in FIG. 15, the audio streams of the main clipAV stream contained in the main clip associated with the obtained number(type=1) and the audio streams of the sub-clip AV stream file containedin the sub clip associated with the obtained number (type=2). If type=1in stream_entry( ) in FIG. 15, the controller 34 can determine that theaudio stream associated with the obtained number is contained in themain clip. If type=2 in stream_entry( ) in FIG. 15, the controller 34can determine that the audio stream associated with the obtained numberis contained in the sub-clip.

In step S77, the controller 34 specifies a desired audio stream. Morespecifically, the controller 34 specifies a desired audio streamcontained in the main clip associated with the obtained number or thesub-clip associated with the obtained number. If it is determined instep S74 that the audio stream associated with the obtain number iscontained in the main clip, the controller 34 specifies thepredetermined audio stream contained in the main clip based oninformation (ref_to_stream_PID_of_mainClip) entered in stream_entry( )as type=1. If it is determined in step S74 that the audio streamassociated with the obtained number is contained in a sub-clip, thecontroller 34 specifies the predetermined audio stream contained in thesub-clip based on information (ref_to_SubPath_id,ref_to_SubPath_entry_id, and ref_to_stream_PID_of_SubClip) entered instream_entry( ) as type=2. The specified audio stream serves as theaudio stream #2 decoded by the first audio decoder 75-2.

In step S78, the controller 34 instructs the storage drive 31 to readthe clip AV stream (main clip AV stream or sub-clip AV stream)corresponding to the clip into which the desired audio stream ismultiplexed. In response to this instruction, the storage drive 31 readsthe target clip AV stream. More specifically, the controller 34instructs the storage drive 31 to read the clip AV stream specified instep S77.

In step S79, the controller 34 instructs the AV decoder 33 to play backthe audio stream from the read clip AV stream. More specifically, thecontroller 34 instructs the audio decoder 75-2 to decode the desiredaudio stream (i.e., audio stream #2) contained in the read clip AVstream.

In step S80, the AV decoder 33 decodes the audio stream (audio stream#2) and outputs it. More specifically, the audio decoder 75-2 of the AVdecoder 33 decodes the audio stream #2 (target audio stream in step S78)and outputs the decoded stream to the mixing processor 98. The audiostream #2 is decoded by the second audio decoder 75-2 in the processingshown in FIG. 30. This means that the audio stream #1 is decoded by theaudio decoder 75-1 in the processing shown in FIG. 29, and the decodedaudio stream #1 is output to the mixing processor 98. The mixingprocessor 98 mixes the audio stream #1 with the audio stream #2, andsupplies the mixed stream to the mixing processor 97. The mixingprocessor 97 then mixes the supplied audio data from the mixingprocessor 98 with the sound data output from the buffer 95, and outputsthe resulting data as an audio signal. Details of step S80 (and step S60in FIG. 20) are given below with reference to the flowchart in FIG. 31.

FIG. 31 illustrates an example of processing for outputting an audiostream by the AV decoder 33, that is, FIG. 31 is a flowchartillustrating details of step S60 in FIG. 29 or step S80 in FIG. 30.

In step S81, the AV decoder 33 determines under the control of thecontroller 34 whether the number of audio stream to be played back isonly one. More specifically, the AV decoder 33 determines under thecontrol of the controller 34 whether the user has selected audio stream#1 and audio stream #2. For example, if an instruction to switch soundfor the audio streams #1 or audio streams #2 in step S52 in FIG. 29 orstep S72 in FIG. 30, respectively, has been given from the user, or ifan instruction to play back the audio stream #1 and audio stream #2 hasbeen given from the user, the AV decoder 33 determines in step S81 thatthe number of audio streams is not one, but two. If an instruction toplay back the audio stream #1 has been given from the user, or if aninstruction to switch sound for the audio streams #1 has been given fromthe user without an instruction to switch sound for the audio streams #2in step S52 in FIG. 29, the AV decoder 33 determines in step S81 thatthe number of audio stream to be played back is only one.

If it is determined in step S81 that the number of audio stream to beplayed back is one, the process proceeds to step S82 in which the firstaudio decoder 75-1 decodes that audio stream, i.e., audio stream #1. Forexample, if the audio stream to be played back is an audio stream of amain clip AV stream, the audio stream selected by the PID filter 55 andselected by the switch 59 is supplied to the first audio decoder 75-1.Then, the first audio decoder 75-1 decodes the audio stream of the mainclip AV stream (in this case, audio stream #1), and supplies the decodedaudio stream #1 to the mixing processor 98. The mixing processor 98 thendirectly outputs the audio data to the mixing processor 97.

If it is determined in step S81 that the number of audio streams to beplayed back is not one, but two, between the two audio streams, theaudio stream #1 is supplied to the audio decoder 75-1 and the audiostream #2 is supplied to the audio decoder 75-2. That is, the switch 59is changed so that the audio stream #1 supplied from the PID filter 55or 56 can be supplied to the first audio decoder 75-1 and so that theaudio stream #2 supplied from the PID filter 55 or 56 can be supplied tothe second audio decoder 75-2.

Then, in step S83, the first audio decoder 75-1 decodes the audio stream#1. For example, if the audio stream #1 to be played back is an audiostream of the main clip AV stream, the audio stream selected by the PIDfilter 55 is selected by the switch 59 and is supplied to the firstaudio decoder 75-1. Then, the first audio decoder 75-1 decodes the mainclip audio stream (audio stream #1). The first audio decoder 75-1supplies the decoded audio stream #1 to the mixing processor 98.

In step S84, the second audio decoder 75-2 decodes the audio stream #2.For example, if the audio stream #2 to be played back is an audio streamof a sub-clip AV stream, the audio stream selected by the PID filter 56is selected by the switch 59 and is supplied to the second audio decoder75-2. Then, the second audio decoder 75-2 decodes the sub-clip audiostream (audio stream #2). The second audio decoder 75-2 supplies thedecoded audio stream #2 to the mixing processor 98. The order of stepsS83 and S84 may be reversed or steps S83 and S84 may be executed inparallel.

In step S85, the mixing processor 98 mixes (combines or superimposes)the audio stream #1 decoded by the first audio decoder 75-1 and theaudio stream #2 decoded by the second audio decoder 75-2. Then, themixing processor 98 supplies the mixed audio data to the mixingprocessor 97.

After step S82 or S85, the process proceeds to step S86. In step S86,the mixing processor 97 mixes the supplied audio data with the sounddata supplied from the buffer 95, and outputs the resulting data. Instep S86 after step S82, the mixing processor 97 mixes the audio datadecoded from the audio stream #1 with the sound data. In step S86 afterstep S85, the mixing processor 97 mixes the audio data, which isgenerated by mixing the audio data decoded from the audio stream #1 withthe audio data decoded from the audio stream #2, with the sound data.Then, the process is completed.

According to the processing shown in FIG. 31, two audio streams can bemixed and played back.

According to the processing discussed with reference to FIG. 31, theselection of the switch 59 in FIG. 25 in step S21 in FIG. 27 can bedetermined. More specifically, if it is determined in step S81 in FIG.31 that the number of audio stream to be played back is one, the switch59 is changed so that the audio stream supplied from the PID filter 55or 56 can be supplied to the first audio decoder 75-1 (outcome of stepS81 is YES). If it is determined in step S81 in FIG. 31 that the numberof audio streams to be played back is two, the switch 59 is changed sothat the audio stream supplied from the PID filter 55 or 56 can besupplied to the second audio decoder 75-2 (outcome of step S81 is YES).

As described above, the controller 34 can control the switching of sound(audio) based on STN_table( ) of PlayItem( ). The controller 34 can alsoselect streams only that can be played back by the playback apparatus 20by referring to_stream_attribute of STN_table( ). Based on STN_table( ),the controller 34 also control two audio streams to be superimposed andplayed back. The controller 34 can also perform control so that theaudio stream #1, which serves as a main stream, is mixed with the audiostream #2, which is a stream of the same type (in this case, an audiostream) of the audio stream #1 and play them back simultaneously.

Although in the processing shown in FIG. 29 audio streams are switchedbased on the audio stream numbers, they may be switched based on theaudio stream IDs (audio_stream_id). In this case, the numbers obtainedby subtracting one from the audio stream numbers are audio stream IDs.

In this embodiment, two audio streams are mixed (combined) and playedback. However, the type of stream is not restricted to audio, andvarious streams can be mixed and played back as long as they are thesame stream type. For example, video streams may be combined and playedback (picture-in-picture display).

The configuration as described above can be used for so-called“picture-in-picture (PinP)” display, and more specifically, a videostream (video stream #1) referred to by a main path is displayed as amain screen and a video stream (video stream #2) referred to by asub-path (or a main path) is displayed inside the main screen as asub-screen.

A stream or a data file, which contains audio or subtitle data,different from a main AV stream, is provided, and the playlist includesa main path and a sub-path. With this configuration, the user can selectfrom streams contained in the main clip and the streams contained in thesub-clips different from the main clip when switching sound orsubtitles.

In a play item in the main path, the stream number definition tabledefining the type of data multiplexed into an AV stream file and thetype of data referred to by a sub-path is provided. Accordingly, streamshaving high extensibility can be implemented.

By referring to stream_attribute of STN_table( ), the playback apparatus20 can sequentially select and play back streams only that can be playedback by the playback apparatus 20.

The processing performed by the playback apparatus 20 can be summarizedas follows.

The playback apparatus 20 obtains a playlist as playback managementinformation. The playlist includes a main path, which is a playback pathindicating the position of a main clip AV stream file containing atleast one stream, and a plurality of sub-paths, each indicating theposition of a sub-clip AV stream file played back in synchronizationwith the main stream file. Based on STN_table( ), the selection of astream to be played back is received. On the basis of STN_table( ),which serves as information for selecting a predetermined stream (forexample, audio stream #1) of the main clip AV stream file and a streamof the same type (for example, audio stream #2) of the main stream file,which is played back in synchronization with the main stream file, theselection of a stream to be played back is received.

In response to an instruction to select two streams (audio streams) ofthe same type, the playback apparatus 20 reads the files containing theselected two streams. The mixing processor 98 then combines the twoaudio streams and the mixing processor 97 (AV decoder 33) plays back(outputs) the combined streams.

With this operation, when two streams, i.e., audio 1 (A_SN=2) and audio5 (A_SN2=2), are selected by the user, as shown in FIG. 32, the audio 1and audio 5 can be mixed (combined) and played back.

In this manner, a playlist includes a main path and sub-paths, and themain path and sub-paths refer to different clips. Accordingly, streamshaving high extensibility can be implemented. Additionally, since onesub-path can refer to a plurality of files (for example, FIG. 8), theuser can select from a plurality of different streams.

A play item of the main path includes the STN_table( ) discussed withreference to FIG. 14 as a table for defining data (for example, audiostreams) multiplexed into an AV stream file referred to by the main pathand data referred to by sub-paths. Thus, streams having highextensibility can be implemented. Additionally, sub-paths can be easilyextended by entering additional data into STN_table( ).

Stream-attribute( ) shown in FIG. 16, which is stream attributeinformation, is provided in STN_table( ). This enables the playbackapparatus 20 to determine whether it has a function of playing back aselected stream. By referring to stream_attribute( ), the playbackapparatus 20 can select streams only that can be played back.

In STN_table( ) (FIG. 14), two stream files of the same type (in thiscase, audio stream files) are defined, and the playback apparatus 20includes two audio decoders, i.e., the first audio decoder 75-1 and thesecond audio decoder 75-2, and the mixing processor 98 for mixing thedecoded audio data. Thus, two streams of the same type can be combinedand played back simultaneously.

A sub-path includes SubPath_type indicating the type of sub-path (suchas audio or subtitles), as shown in FIG. 11, Clip_Information_file_nameindicating the name of the sub-clip referred to by the sub-path, asshown in FIG. 12, and SubPlayItem_IN_time and SubPlayItem_OUT_timeindicating the IN point and the OUT point of the clip referred to by thesub-path, as shown in FIG. 12. Accordingly, data referred to by thesub-path can be precisely specified.

The sub-path also includes sync_PlayItem_id (for example,sync_PlayItem_id shown in FIGS. 7 and 8), which is information forspecifying the AV stream file on the main path so that the sub-path canbe played back simultaneously with the main path, andsync_start_PTS_of_PlayItem (for example, sync_start_PTS_of_PlayItem inFIGS. 7 and 8), which is the time on the main path at which the IN pointof the data referred to by the sub-path is started simultaneously on thetime axis of the main path. Accordingly, data (file) referred to by the.sub-path can be played back, as shown in FIGS. 7 and 8, insynchronization with the main clip AV stream file referred to by themain path.

The data read by the storage drive 31 shown in FIG. 25 may be datarecorded on a recording medium, such as a DVD, or an HDD, datadownloaded via a network (not shown), or a combination of such data. Forexample, data may be played back based on a playlist and a clipincluding a sub-clip AV stream recorded on an HDD and a clip including amain clip AV stream recorded on a DVD. Alternatively, if a playlistreferring to a clip recorded on a DVD as a clip containing a sub-clip AVstream and a clip containing a main clip AV stream are recorded on anHDD, based on the playlist recorded on the HDD, the main clip AV streamand the sub-clip AV stream may be read from the HDD and the DVD,respectively, and are played back.

To mix and play back two audio streams, the first audio decoder 75-1decodes the audio stream #1, while the second audio decoder 75-2 decodesthe audio stream #2. A determination may be made in step S54 in FIG. 29or step S74 in FIG. 30 as to whether the coding type of the audio stream#1 and audio stream #2 is the same (from example, Dolby AC-3 audio inFIG. 17). The reason for this is as follows. If the coding type is thesame, two streams which are in process of being decoded by the firstaudio decoder 75-1 and the second audio decoder 75-2 can be mixed by themixing processor 98 since the data type of audio streams which are beingdecoded is the same.

In the above-described example, the audio stream #1 decoded by the firstaudio decoder 75-1 and the audio stream #2 decoded by the second audiodecoder 75-2 can be selected separately by the user. Alternatively,combinations of audio streams #1 and audio streams #2 that can be mixedmay be determined, and the user is instructed to select a combination ofaudio streams to be mixed. Two examples of this case are described belowwith reference to FIGS. 33 through 37.

The first example is discussed below. FIG. 33 illustrates a secondexample of the syntax of STN_table( ) (second STN_table( )) whencombinations of audio streams #1 and audio streams #2 are defined. InFIG. 33, portions similar to those in FIG. 14 are not explained.

In the FOR loop of the audio stream ID2 (audio_stream_id2),audio_stream_id2 is assigned from 0 to one audio elementary streamspecified for each stream entry( ). In this case, for audio_stream_id2,in addition to stream_entry( ) and stream_attributes( ), a new field,i.e., Combination_of_Primary_and_Secondary, is defined.Combination_of_Primary and_Secondary is information for definingcombinations of audio streams #1 (primary streams) and audio streams #2(secondary streams). That is, information indicating which audio streams#1 can be combined with audio streams #2 represented by the audio streamID2 (audio_stream_id2) is defined in the FOR loop of the audio streamID2. In other words, audio streams #2 that can be combined with audiostreams #1 can be defined in Combination_of_Primary_and_Secondary.Instead of defining audio streams ID2 to be combined with audio streamsID1 in the FOR loop of the audio streams ID1, audio streams ID1 andaudio streams ID2 are defined separately, and combination of audiostreams #1 and audio streams #2 are defined in the FOR loop of the audiostreams ID2. With this configuration, even if the number of audiostreams ID1 to be registered is fixed, combinations of audio streams ID1with audio streams ID2 do not count toward the number of registrations.Thus, the number of audio streams that can be registered can be usedeffectively.

As described with reference to FIG. 14, instead of the audio stream ID2(audio_stream_id2), the audio stream number 2 (audio_stream_number2) maybe used, in which case, audio_stream_number 2 is assigned from 1. Thatis, the number obtained by adding one to audio_stream_id2 isaudio_stream_number2. The number is assigned from 1 since the audiostream number 2 is the number that can be seen from the user whenswitching sound.

An example of the bitmap syntax of Combination_of_Primary_and_Secondaryshown in FIG. 33 is described below with reference to FIG. 34.

The bitmap syntax of Combination_of_Primary_and_Secondary shown in FIG.34 is 32 bits. In FIG. 34, audio_stream_id indicates the audio_stream_id(audio stream ID) defined in the fourth STN_table( ) in FIG. 33, and theindicator designates a flag indicating audio_stream_id specifying theaudio stream #1 that can be combined with the audio stream #2 specifiedby the corresponding audio_stream_id2 (audio stream ID2). That is, by acombination of audio_stream_id and indicator, audio_stream_id of theaudio stream #1 that can be combined with the audio stream #2represented by audio_stream_id2 can be specified.

As Combination_of_Primary_and_Secondary specified in the FOR loop ofaudio_stream_id2 in FIG. 33, Combination_of_Primary_and_Secondary isdefined for each audio_stream_id2, and the audio stream #1 that can becombined with a certain audio stream #2 represented by audio_stream_id2can be specified by audio_stream_id designated by the indicator.

More specifically, if the indicator is 0, the correspondingaudio_stream_id2 is not associated with the audio stream #1 specified byaudio_stream_id. If the indicator is 1, the correspondingaudio_stream_id2 is associated with the audio stream #1 specified byaudio_stream_id.

FIG. 34 shows that two audio streams (audio streams #1) specified byaudio_stream_id=0 and audio_stream_id=1 can be combined with the audiostream #2 specified by audio_stream_id2 (audio stream ID2).

Although in FIG. 34 the audio stream #1 is specified by audio_stream_id,the audio stream number may be used, in which case, the audio streamnumber is assigned from 1.

Since Combination_of_Primary_and_Secondary is defined by the 32-bitbitmap syntax, as shown in FIG. 34, an audio stream #2 can be definedfor each of the 32 audio streams #1.

According to FIGS. 33 and 34, combinations of audio streams #1 and audiostreams #2 can be defined by using audio_stream_id, audio_stream_id2,and Combination_of_Primary_and_Secondary. That is, the user can select acombination of audio streams that can typically be played back withoutselecting inconsistent combinations.

A specific example is discussed below with reference to FIG. 35illustrating an example of a stream number table indicating audio streamnumbers and subtitle stream numbers. A description of subtitle streamnumbers (sub-pictures) is similar to that in FIG. 24, and an explanationthereof is thus omitted.

In FIG. 35, each of the audio streams #1 (audio streams specified byaudio_stream_id) entered in the STN_table( ) of PlayItem( ) forming themain path of a playlist is provided with A_SN.

More specifically, audio 2 is assigned to A_SN=1, audio 1 is assigned toA_SN=2, and audio 3 is assigned to A_SN=3.

In this case, audio 4 (audio_stream_id2=0, i.e., audio stream number 2is 1) can be combined with audio 2 associated with A_SN=1. Audio 4(audio_stream_id2=1, i.e., audio stream number 2 is 1) and audio 5(audio_stream_id2=1, i.e., audio stream number 2 is 2) can be combinedwith audio 1 associated with A_SN=2.

More specifically, for audio 4 (audio_stream_id2=0), in the bitmapsyntax of Combination_of_Primary_and_Secondary in FIG. 34, the indicatorvalues for audio_stream_id=0 and audio_stream_id=1 are 1, and theindicator values for audio_stream_id=2 through audio_stream_id=31 areall 0. For audio 5 (audio_stream_id2=1), in the bitmap syntax ofCombination_of_Primary-and_Secondary in FIG. 34, the indicator value foraudio_stream_id=1 is 1, and the indicator values for audio_stream_id=0,and audio_stream_id=2 through audio_stream_id=31 are all 0.

The user selects audio stream #1 to be played back from audio streamsprovided with A_SN, and selects audio stream #2 from audio streamsindicated at the right side in FIG. 35. In the example in FIG. 35, ifthe user selects audio 2 (A_SN=1) as the audio stream #1, the audiostream #2 that can be mixed with the audio stream #1 is only audio 4,and thus, the user determines whether to select audio 4 to be combinedwith audio 2. In FIG. 35, audio 4 associated with audio 2 is indicatedby X, which means that it is not combined with audio 2. If it isswitched to O, audio 4 can be combined with audio 2.

In FIG. 35, if the user selects audio 1 (A_SN=2) as audio stream #1, theaudio stream #2 that can be mixed with audio #1 can be selected fromaudio 4 and audio 5 indicated at the right side in FIG. 35. Accordingly,the user determines whether to select audio 4 or audio 5. In FIG. 35,audio 4 and audio 5 associated with audio 1 are indicated by X, whichmeans that neither of them is combined with audio 1. If one of them isswitched to O, audio 4 or audio 5 can be combined with audio 1.

A specific example of an instruction to select audio streams is givenbelow. If the user gives an instruction to switch audio streams whileselecting audio 2 associated with A_SN=1, the playback operation isswitched to a combination of audio 2 and audio 4 (audio 4 is changed toO in FIG. 35). If the user further gives an instruction to switch audiostreams, the playback operation is switched to audio 1 associated withA_SN=2 (audio 4 is changed to X in FIG. 35). If the user further givesan instruction to switch audio streams, the playback operation isswitched to a combination of audio 1 and audio 4 (audio 4 is changed toO). If the user further gives an instruction to switch audio streams,the playback operation is switched to a combination of audio 1 and audio5 (audio 4 is changed to X and audio 5 is changed to O in FIG. 35).

By switching the selection of audio streams to be played back, the usercan select a combination of audio 1 associated with A_SN=2 and audio 5,as shown in FIG. 36. Accordingly, audio 1 (audio stream #1) and audio 5(audio stream #2) can be mixed and played back.

By using audio_stream_id, audio_stream_id2, andCombination_of_Primary_and_Secondary, a combination of audio stream #1and audio stream #2 can be defined. This enables the user to select acombination of audio streams that can typically be played back withoutselecting inconsistent combinations. That is, in the example in FIG. 35,the user can select audio streams without selecting an inconsistentcombination, such as audio 2 and audio 5.

In other words, in the second STN_table( ) (FIG. 33) in PlayItem( ), acombination of the audio stream #1 decoded by the first audio decoder75-1 and the audio stream #2 decoded by the second audio decoder 75-2shown in FIG. 25 can be defined by usingCombination_of_Primary_and_Secondary. Accordingly, two audio streams canbe mixed and played back. That is, from a plurality of types of streams,streams of the same type (in this case, audio streams) can be mixed(combined or superimposed) and played back simultaneously.

With this configuration, the user can select audio streams from apredetermined combination without the need to individually select twoaudio streams.

A description is now given, with reference to FIG. 37, a second examplein which the user is instructed to select a combination of audio stream#1 and audio stream #2 from defined combinations. In other words, FIG.37 shows a second example in which audio streams that can be mixed withaudio streams #1 are defined as audio streams #2.

FIG. 37 illustrates a third example of the syntax of STN_table( ) (thirdSTN_table( )) for defining combinations of audio streams #1 and audiostreams #2. In FIG. 37, portions similar to those in FIG. 14 or 33 notexplained.

In FIG. 37, in the FOR loop of the audio stream ID2 (audio_stream_id2),audio_stream_id2 is assigned from 0 to one audio elementary stream whoserecording position is specified for each stream_entry( ). In this case,number_of combinations is defined for audio stream_id2, and in the FORstatement after number_of_combinations, the same number ofaudio_stream_id as the number of number_of_combinations is given. Thenumber_of_combinations and the FOR statement afternumber_of_combinations are information for defining combinations ofaudio streams #1 and audio streams #2, and the number of audio streams#1 that can be combined with the audio streams #2 specified byaudio_stream_id2 is the number_of_combinations. The audio_stream_idspecifying the audio streams #1 that can be combined with the audiostreams #2 specified by the audio_stream_id2 is defined in the FORstatement after number_of_combinations.

That is, unlike the fourth STN_table( ) in FIG. 33, in the FOR statementof audio stream ID2 (audio_stream_id2) in the third STN_table( ) in FIG.37, the number of audio streams #1 that can be combined with the audiostreams #2 specified by the audio stream ID2 is defined bynumber_of_combinations, and in the FOR statement afternumber_of_combinations, audio_stream_id specifying the audio streams #1is directly defined.

In this manner, in the third STN_table( ), information indicating whichaudio streams #1 are combined with the audio streams #2 specified by theaudio stream ID2 (audio_stream_id2) is defined in the FOR statementafter number_of_combinations of the audio stream ID2. In other words, inthe FOR statement after number_of_combinations of the audio stream ID2,the audio streams #2 that can be combined with the audio streams #1 aredefined.

As discussed with reference to FIG. 14 or 33, instead of the audiostream ID2 (audio_stream_id2), the audio stream number 2(audio_stream_number2) may be used. Instead of the audio stream number 2(audio_stream_id), the audio stream number (audio_stream_number) may beused. That is, the audio stream number may substitute theaudio_stream_id defined in the FOR statement afternumber_of_combinations.

In FIG. 37, by using number_of_combinations and the subsequent FORstatement, combinations of audio streams #1 and audio streams #2 can bedefined. That is, the user can select a combination of audio streamsthat can typically be played back without selecting inconsistentcombinations.

A specific example of the stream number table is similar to thatdiscussed with reference to FIGS. 35 and 36.

If the stream number table shown in FIG. 35 is applied to the thirdSTN_table( ) in FIG. 37, as the audio streams #1 that can be combinedwith audio 4 (audio_stream_id2=0, i.e., audio stream number 2 is 1),audio 2 (audio_stream_id=0) associated with A_SN=1 and audio 1(audio_stream_id=1) associated with A_SN=2 are defined. In this case,the number_of_combinations corresponding to audio_stream_id2=0 is 2, andthe defined audio_stream_id is audio_stream_id=0 and audio_stream_id=1.Also, as the audio streams #1 that can be combined with audio 5(audio_stream_id2=1, i.e., audio stream number 2 is 2), audio 1(audio_stream_id=1) associated with A_SN=2 is defined. In this case, thenumber_of_combinations corresponding to audio_stream_id2=1 is 1, and thedefined audio_stream_id is audio_stream_id=1.

By switching audio streams to be played back shown in FIG. 35, the userselects, for example, a combination of audio 1 and audio 5 associatedwith A_SN=2, as shown in FIG. 36. Then, the audio 1 (audio stream #1)and audio 5 (audio stream #2) can be mixed and played back.

As described above, by using number_of_combinations and the subsequentFOR statement, combinations of audio streams #1 and audio streams #2 canbe defined. Then, the user can select a combination of audio streamsthat can typically be played back without selecting inconsistentselections. For example, in FIG. 35, an inconsistent combination, e.g.,audio 2 and audio 5, is not defined.

In other words, in the third STN_table( ) (FIG. 37) in PlayItem( ),combinations of audio streams #1 decoded by the first audio decoder 75-1and audio streams #2 decoded by the second audio decoder 75-2 aredefined in number_of_combinations and the subsequent FOR statement.Thus, two audio streams can be mixed and played back. That is, from aplurality of types of streams, streams of the same type (in this case,audio streams) can be mixed (combined or superimposed) and played backsimultaneously.

By using the third STN_table( ), the user can select audio streams to beplayed back from a predetermined combination without the need toindividually select two audio streams.

FIG. 38 illustrates a fourth example of the syntax of STN_table( )(fourth STN_table( )) defining combinations of audio streams #1 andaudio streams #2. In FIG. 38, portions similar to those in FIG. 14, 33,or 37 are not explained.

In the FOR loop of the audio stream ID (audio_stream_id) in FIG. 38,audio_stream id is assigned from 0 to one audio stream #1 specified foreach stream_entry( ), as in the first STN_table( ) shown in FIG. 14. Thestream_attributes( ) after the FOR loop of the audio stream ID issimilar to that in the third STN_table( ) in FIG. 14.

In the fourth STN_table( ) in FIG. 38, however, the followinginformation for defining combinations of audio streams #1 and audiostreams #2 is included in the FOR loop of the audio stream ID(audio_stream_id). If number_of_audio_stream2_entries is not 0 (if(number_of_audio_stream2_entries!=0), number_of audiostream2_ref_entries is given. The number_of_audio_stream2_ref_entriesindicates the number of audio streams #2 that can be combined with theaudio streams #1 specified by audio_stream_id. The audio_stream2_id_refspecifying the audio streams #2 that can be combined with the stream #1is defined after the FOR statement ofnumber_of_audio_stream2_ref_entries.

As in the other examples of STN_table( ), the audio stream number 2 ref(audio_stream_number2_ref) may be used instead of the audio stream ID2ref (audio_stream_id2_ref), and the audio stream number(audio_stream_number) may be used instead of the audio stream ID(audio_stream_id).

In this manner, combinations of the audio streams #1 and the audiostreams #2 can be defined by referring to the fourth STN_table( ) inFIG. 38. Accordingly, the user can select a combination of audio streamsthat can typically be played back without selecting inconsistent audiostreams.

As stated above, an application format of data recorded on a recordingmedium installed in the playback apparatus of an embodiment of thepresent invention is formed of two layers, i.e., a playlist layer and aclip layer. The playlist includes a main path having at least one playitem (sequential if there are more than one), and at least one sub-pathhaving at least one sub-play item (may be sequential or non-sequentialif there are more than one) disposed in parallel with the main path.

With this configuration, as shown in FIG. 39, content, such as a movie,corresponding to AV streams (a video stream 311 indicated by primaryvideo in FIG. 39 and an audio stream 312 indicated by primary audio inFIG. 39) referred to by the main path can be played back in a mainscreen 301, and content different from the AV streams referred to by themain path, for example, director's commentaries on the movie (a videostream 313 indicated by secondary video in FIG. 39 and an audio stream314 indicated by secondary audio in FIG. 39) corresponding to AV streamsreferred to by a sub-path, can be played back in a sub-screen 302contained in the main screen 301.

That is, different content items can be simultaneously played back inthe main screen 301 and the sub-screen 302.

This technique is referred to as the “picture-in-picture” technique.

The sound corresponding to the audio stream (primary audio) 312 and thesound corresponding to the audio stream (secondary audio) 314 can bemixed and played back, as discussed above.

The real subject to be played back is sound or images corresponding tostreams, as stated above. For the sake of simple description, however,it may be said that “a predetermined stream is played back” in thefollowing description.

To implement an application using the picture-in-picture technique, thefollowing syntax, for example, is necessary. In this embodiment, thenumber of video streams (hereinafter referred to as “primary videostreams”, for example, the video stream 311 shown in FIG. 39 is referredto as the “primary video stream”) defined by video_stream_id inSTN_table( ) shown in FIGS. 40 and 41 is one. By considering this fact,if a syntax defining combinations of streams that can be played backsimultaneously with the primary video stream is prepared, thepicture-in-picture technique, i.e., an application using thepicture-in-picture technique, can be implemented.

In this embodiment, as the streams that can be played backsimultaneously with the primary video stream by the picture-in-picturetechnique, the following four streams, i.e., the first through fourthtypes of streams, are prepared.

The streams of the first type are audio streams defined byaudio_stream_id in STN_table( ) shown in FIGS. 40 and 41, that is, theabove-described audio streams #1 (hereinafter referred to as “primaryaudio streams”, for example, the audio stream 312 shown in FIG. 39 isreferred to as the “primary audio stream”).

The streams of the second type are video streams defined byvideo_stream_id2 in STN_table( ) shown in FIGS. 40 and 41 (hereinafterreferred to as “secondary video streams”, for example, the video stream313 shown in FIG. 39 is referred to as the “secondary video stream”).

The streams of the third type are audio streams defined byaudio_stream_id2 in STN_table( ) shown in FIGS. 40 and 41, that is, theabove-described audio streams #2, (hereinafter referred to as “secondaryaudio streams”, for example, the audio stream 314 shown in FIG. 39 isreferred to as the “secondary audio stream”).

The streams of the fourth type are text subtitle streams (txtST) orstreams (PG and presentation graphics streams) obtained byrun-length-coding bitmap subtitles, such as DVD sub-pictures, referredto by a sub-path. For example, a subtitle stream 315 in FIG. 39 is anexample of the streams of the fourth type. The streams of the fourthtype (txtST and PG) are referred to as “subtitle streams”. It is notnecessary that subtitle streams be displayed in the sub-screen, and maybe displayed at any position in the main screen. Accordingly, thesubtitle stream 315 is outside the sub-screen 302 in FIG. 39.

As discussed above, to implement an application using thepicture-in-picture technique, it is necessary to define combinations ofstreams, i.e., secondary video streams, primary audio streams, secondaryaudio streams, and subtitle streams, that can be played backsimultaneously with a primary video stream.

By defining a plurality of combinations, not only the primary videostream 311 or the primary audio stream 312 displayed on the main screen301, secondary video streams or subtitle streams displayed in thesub-screen 302 can be easily switched. An example of the switchingoperation is discussed below with reference to FIGS. 42 and 43.

The definition of combinations of streams that can be played backsimultaneously with a primary video stream can be provided in, forexample, a fifth STN_table( ) shown in FIGS. 40 and 41. FIGS. 40 and 41illustrate a fifth example of the syntax of STN_table( ) (fifthSTN_table( )) for defining combinations of secondary video streams,primary audio streams, secondary audio streams, and subtitle streamsthat can be played back together with a primary video stream. In FIGS.40 and 41, portions similar to those of the other examples of STN_table() are not explained.

In the example shown in FIGS. 40 and 41, combinations of secondary videostreams, primary audio streams, secondary audio streams, and subtitlestreams that can be played back together with a primary video stream aredefined as follows. First, at least one secondary video stream that canbe played back simultaneously with the primary video stream is defined.Then, audio streams (primary audio streams and secondary audio streams)and subtitle streams that can be played back simultaneously with each ofthe secondary video streams are defined.

More specifically, in FIG. 40, number_of_video_stream2_entries indicatesthe number of streams provided with video_stream_id2 and entered(registered) in the fifth STN_table( ). The video_stream_id2 isinformation for identifying secondary video streams, andvideo_stream_number2 is the secondary video stream number that can beseen from the user when switching video.

In FIG. 41, in the FOR loop of the video stream ID2 (video_stream_id2),video_stream_id2 is assigned from 0 to one secondary video elementarystream (serves as a secondary video stream) specified for eachstream_entry( ).

For video_stream_id2, the number_of_Audio_combinations_for_video2 isprovided. In the subsequent FOR statement, the same number ofaudio_stream_id and audio_stream_id2 as that ofnumber_of_Audio_combinations_for_video2 are provided. Thenumber_of_Audio_combinations_for_video2 and the subsequent FOR statementserve as information for defining combinations of primary audio streamsspecified by audio_stream_id and the secondary audio streams specifiedby audio_stream_id2 that can be played back simultaneously with thesecond video stream. The number of audio streams (primary audio streamsand secondary audio streams) that can be combined with the secondaryvideo stream specified by video_stream_id2 isnumber_of_Audio_combinations_for_video2. Then, in the FOR statementafter number_of_Audio_combinations_for_video2, audio_stream_idspecifying the primary audio streams and audio_stream_id2 specifying thesecondary audio streams that can be combined with the secondary videostream are defined.

For the same video_stream_id2,number_of_Subtitle_combinations_for_video2 is provided. In thesubsequent FOR statement, the same number of PG_textST_stream_id as thenumber of number_of_Subtitle_combinations for_video2 are provided. Thenumber_of_Subtitle_combinations_for_video2 and the subsequent FORstatement serve as information for defining combinations of subtitlestreams that can be played back simultaneously with the secondary videostream. The number of subtitle streams that can be combined with thesecondary video stream specified by video_stream_id2 isnumber_of_Subtitle_combinations_for video2. Then, in the FOR statementafter number_of_Subtitle_combinations_for_video2, PG_textST_stream_idspecifying subtitle streams that can be combined with the secondaryvideo stream specified by video_stream_id2 is defined.

As in the other examples of STN_table( ), the audio stream number(audio_stream_number) may be used instead of audio stream_id, and theaudio stream number 2 may be used instead of audio_stream_id2. The sameapplies to video streams and subtitle streams.

According to the fifth STN_table( ) shown in FIGS. 40 and 41, secondaryvideo streams that can be played back together with the primary videostream can be defined by video_stream_id2. Then, by usingvideo_stream_id2, audio_stream_id, audio_stream_id2, andPG_textST_stream_id, primary audio streams, secondary audio streams, andsubtitle audio streams that can be played back simultaneously with eachof the secondary video streams can be defined. That is, combinations ofthe secondary video streams, primary audio streams, secondary audiostreams, and subtitle audio streams that can be played backsimultaneously with the primary video stream can be defined.

With this configuration, inconsistent combinations of the primary videostream and secondary video streams, primary audio streams, secondaryaudio streams, and subtitle audio streams that can be played backsimultaneously with the primary video stream are not defined.Accordingly, the user can easily select a stream that can be combinedwith the primary video stream.

A specific example is described below with reference to FIGS. 42 and 43.FIG. 42 illustrates a stream number table, provided to users, indicatingcombinations of sound numbers (audio signals) associated with primaryaudio streams or secondary audio streams, video numbers (video signals)associated with secondary video streams, and subtitle numbers (subtitlesignals) associated with subtitle streams when the fifth STN_table( )shown in FIGS. 40 and 41 is used. The sound numbers and subtitle numbersare similar to those discussed with reference to FIG. 24 or 35, and anexplanation thereof is thus omitted.

In FIG. 42, each of the secondary video streams specified byvideo_stream_id2 entered in the fifth STN_table( ) of a play itemforming the main path of the playlist is provided with V2_SN (video2stream number (secondary video stream number)).

More specifically, video 2 is assigned to V2_SN=1, and video 1 isassigned to V2_SN=2.

In this case, for video 2 associated with V2_SN=1, audio 2 (primaryaudio stream entered in audio_stream_id in the FOR statement whenvideo_stream_id2 specifies video 2 in FIG. 41) as a primary audiostream, audio 4 (secondary audio stream entered in audio_stream_id2 inthe FOR statement when video_stream_id2 specifies video 2 in FIG. 41) asa secondary audio stream, and sub-picture 3 (subtitle stream entered inPG_textST_stream_id in the FOR statement when video_stream_id2 specifiesvideo 2 in FIG. 41) as a subtitle stream can be combined.

For video 1 associated with V2_SN=2, audio 1 (primary audio streamentered in audio_stream_id in the FOR statement when video_stream_id2specifies video 1 in FIG. 41) as a primary audio stream, audio 4 oraudio 5 (each of secondary audio streams entered in audio_stream_id2 inthe FOR statement when video_stream_id2 specifies video 1 in FIG. 41) asa secondary audio stream, and sub-picture 1 (subtitle stream entered inPG_textST_stream_id in the FOR statement when video_stream_id2 specifiesvideo 1 in FIG. 41) as a subtitle stream can be combined.

In the FOR statement when video_stream_id2 is video 1 in FIG. 41, afirst combination and a second combination are defined as combinationsof audio streams that can be played back simultaneously with video 1associated with V2_SN=2. The first combination is audio 1 as the primaryaudio stream and audio 4 as the secondary audio stream. The secondcombination is audio 1 as the primary audio stream and audio 5 as thesecondary audio stream.

When the stream number table shown in FIG. 42 is provided (how toprovide to the user is not restricted), the user first selects one ofvideo 2 (VS_SN=1) or video 1 (VS_SN=2) as the secondary video streamassociated with video, for example, director's commentaries that areplayed back simultaneously with a movie, as the secondary video streamcorresponding to video displayed on the sub-screen (sub-screen 302 inFIG. 39).

If, for example, the video 2 (VS_SN=1) is selected as the secondaryvideo stream, the combination of primary and secondary audio streams andsubtitle streams that can be played back at the same time with video 2is, as shown in FIG. 42, the combination of audio 2, audio 4, andsub-picture 3 only. Accordingly, when video 2 (VS_SN=1) is selected asthe secondary video stream, the user does not perform selection anyfurther.

On the other hand, if, for example, video 1 (VS_SN=2), is selected asthe secondary video stream, as the combinations of primary and secondaryaudio streams and subtitle streams that can be played back at the sametime with video 1 is, as shown in FIG. 43, there are two combinations,i.e., a first combination of audio 1, audio 4, sub-picture 1 and asecond combination of audio 1, audio 5, and sub-picture 1. Accordingly,when video 1 (VS_SN=2) is selected, the user can select one of the firstcombination and the second combination.

More specifically, in a manner similar to the selection operationdiscussed with reference to FIG. 35, when the user selects a stream tobe played back simultaneously with video 1 (VS_SN=2), the user changesthe symbol X to O, and when the user does not select that stream, theuser maintains the symbol X. As discussed with reference to FIG. 35, Ois a symbol indicating that the user has selected the correspondingstream to be played back, and X is a symbol indicating that the user hasnot selected the corresponding stream to be played back.

FIG. 43 illustrates an example in which the first combination of audio1, audio 4, and sub-picture 1 has been selected. More specifically,since audio 1 is selected, as shown in FIG. 43, as the primary audiostream that is played back simultaneously with video 1 (V2_SN=2), theselection state of audio 1 is changed from X to O. Since audio 4 isselected as the secondary audio stream that is played backsimultaneously with video 1, the selection state of audio 4 is changedfrom X to O. In contrast, audio 5 is not selected, the selection stateof audio 5 is maintained at X. Since sub-picture 1 is selected as thesubtitle stream that is played back simultaneously with video 1, theselection state of sub-picture 1 is changed from X to O.

According to the above-described series of selection operations, video1, audio 1, audio 4, and sub-picture 1 are selected and are ready to beplayed back with the main video (primary video stream).

In the above-described example, as the selection operation for streamsthat can be played back simultaneously with a primary video stream, asecondary video stream is selected first, and then, a primary audiostream, a secondary audio stream, and a subtitle stream are selectedbased on the secondary video stream.

However, the selection operation is not restricted to the above type.For example, a primary audio stream may be selected first, and then, asecondary video stream, a secondary audio stream, and a subtitle streammay be selected. More specifically, in the stream number table shown inFIG. 43, audio 2 associated with A_SN=1, audio 1 associated with A_SN=2,or audio 3 associated with A_SN=3 is first selected as the primary audiostream, and then, a secondary video stream, a secondary audio stream,and a subtitle stream may be selected, as in the selection operationdiscussed with reference to FIG. 35.

Alternatively, a subtitle stream may be selected first, and then, aprimary audio stream, a secondary video stream, and a secondary audiostream may be selected. More specifically, in the stream number tableshown in FIG. 43, sub-picture 3 associated with S SN=1, sub-picture 1associated with S_SN=2, or sub-picture 2 associated with S_SN=3 is firstselected as the subtitle stream, and then, a secondary video stream, aprimary audio stream, and a secondary audio stream are selected althoughthis selection operation is not shown in FIG. 43.

In this embodiment, the user is prohibited to switch secondary audiostreams. Accordingly, in the example in FIG. 43, the secondary audiostreams are not provided with A_SN. That is, audio 1, audio 2, and audio3 are used as primary audio streams, and audio 4 and audio 5 are used assecondary audio streams.

If the picture-in-picture technique is implemented by using the syntaxof the fifth STN_table( ) shown in FIGS. 40 and 41, a playlist shown inFIG. 44 can be generated if Subpath_type shown in FIG. 11 is used.

In FIG. 44, a video stream and an audio stream included in a clip AVstream-0 (main clip AV stream) referred to by play item 1 (PlayItem-1)forming the main path are used as the primary video stream and theprimary audio stream, respectively. In the example in FIG. 39, the videostream and the audio stream contained in the clip AV stream-0 are theprimary video stream 311 and the primary audio stream 312, respectively.The primary video stream 311 is played back in the main screen 301, andat the same time, the primary audio stream 312 is played back (output).

A secondary video stream contained in a clip AV stream-1 (sub-clip AVstream) referred to by a sub-play item (SPI) contained in sub-path 1 isused as the secondary video stream, and a secondary audio streamcontained in the clip AV stream-1 (sub-clip AV stream) referred to by asub-play item (SPI) contained in sub-path 2 is used as the secondaryaudio stream. In the example in FIG. 39, the secondary video stream andthe secondary audio stream contained in the main clip AV stream-1 arethe secondary video stream 313 and the secondary audio stream 314,respectively. The secondary video stream 313 is played back in thesub-screen 302, and at the same time, the secondary audio stream 314 isplayed back (output).

Playing back the primary audio stream contained in the main clip AVstream-0 in the main screen 301 and playing back the secondary audiostream contained in the sub-clip AV stream-1 in the sub-screen 302 meansthat the two audio streams are mixed and played back, as describedabove.

As described above, in the example in FIG. 44, the example shown FIG. 11is used as SubPath_type, and as a result, the picture-in-picturetechnique is implemented by the main path, sub-path 1, and sub-path 2.

In the example in FIG. 44, the secondary video stream and the secondaryaudio stream that are played back simultaneously with the primary videostream contained in the main clip AV stream-0 are defined by differentsub-paths, i.e., the sub-path 1 and sub-path 2, even though they arecontained in the same clip AV stream-1. This is because, in FIG. 11,only sub-path types indicating that only one elementary stream (ES) canbe referred to by each sub-path are prepared. That is, in SubPath_typein FIG. 11, one sub-path type is assigned to each ES of a plurality ofESs, such as audio, IG, text, and video ESs, regardless of whether theyare contained in the same clip AV stream file.

Accordingly, by the use of SubPath_type shown in FIG. 11, if there aretwo or more ESs to be played back, such ESs are referred to by differentsub-paths, i.e., they are defined as different sub-play items.

In this case, the two or more ESs should define certain information,such as SubPlayItem_IN_time and SubPlayItem_OUT_time, separately fromeach other even though such information is the same since they arecontained in the same clip AV stream file. As a result, the information,such as SubPlayItem_IN_time and SubPlayItem_OUT_time, becomes redundant.

Additionally, a sub-path should be defined for each elementary path tobe played back, which makes the structure of the playlist complicated.

Moreover, in this embodiment, a restriction is imposed on the playbackapparatus (playback apparatus 20 shown in FIG. 25 or playback apparatus401 shown in FIG. 49) such that it can read only two transport streams(TSs) (i.e., TSs contained in two clips) simultaneously. Under thisrestriction, when playing back a playlist having a complicatedstructure, the playback apparatus cannot decide immediately whichsub-path should be combined with the main path defined in the playlist.In other words, to decide a combination of the main path and a sub-path,processing becomes complicated.

Accordingly, to solve the above-described problems, in an embodiment ofthe present invention, a sub-path type that allows a plurality of ESs tobe handled, i.e., that allows a plurality of ESs to be referred to atthe same time, is added as SubPath_type. An example of such SubPath_typeis shown in FIG. 45.

That is, in the example in FIG. 45, sub-path types that can solve theabove-described problems are added to the sub-path types shown in FIG.11.

In FIG. 45, SubPath_type=0 through SubPath_type=4 are the same as thoseof FIG. 11, and an explanation thereof is thus omitted.

However, in the meaning of SubPath_type=2 through SubPath_type=4 in FIG.45, “out-of-mux”, which is not explained in FIG. 11, is contained. The“out-of-mux” means that a TS containing the ES referred to by a sub-pathis different from a TS containing the ES referred to by the main path,that is, the ES referred to by a sub-path is not multiplexed into the TScontained in a play item referred to by the main path. Such a sub-pathtype is referred to as a “main-path-TS non-multiplexed type”.

As in SubPath_type=2 or 3, when the ES referred to by the main path isnot synchronized with the ES referred to by a sub-path, such a sub-pathtype is hereinafter referred to as an “AV non-synchronized type”. On theother hand, as in SubPath_type=4 or 5, when the ES referred to by themain path is synchronized with the ES referred to by a sub-path, such asa sub-path type is hereinafter referred to as an “AV synchronized type”.

SubPath_type=5 indicates “out-of-mux and AV synchronized type of one ormore elementary streams path (primary audio/PG/IG/secondary audio path)”and “out-of-mux and AV synchronized type of picture-in-picturepresentation path which contains one or more elementary stream paths”.That is, SubPath_type=5 is the main-path-TS non-multiplexed type and AVsynchronized type of at least one elementary stream path (primaryaudio/PG/IG/secondary audio path) or a picture-in-picture presentationpath.

That is, SubPath_type=5 encompasses the types indicated bySubPath_type=5 and SubPath_type=6 shown in FIG. 11, and thus includesthe secondary audio presentation path (path for referring to thesecondary audio stream) and the secondary video presentation path (pathfor referring to the secondary video stream).

The picture-in-picture presentation path includes at least one pathreferring to a primary audio stream, a secondary video stream, asecondary audio stream, and a subtitle stream that is combined with apredetermined video stream.

SubPath_type=6 indicates “out-of-mux and AV non-synchronized type ofpicture-in-picture presentation path which contains one or moreelementary stream paths”. That is, SubPath_type=6 is the main-path-TSnon-multiplexed type and AV non-synchronized type of apicture-in-picture presentation path (including at least one ES).

SubPath_type=7 indicates “in-mux type and AV synchronized type ofpicture-in-picture presentation path which contains one or moreelementary stream paths”. In this case, “in-mux” indicates that a TScontaining the ES referred to by a sub-path is the same sub-path type asa TS containing at least one ES referred to by the main path. In otherwords, the main clip AV stream and a sub-clip AV stream are contained inthe main TS included in the main clip. Such a type is referred to as the“main-path-TS multiplexed type”.

That is, SubPath_type=7 is the main-path-TS multiplexed type and AVsynchronized type of a picture-in-picture path (including at least oneES).

SubPath_type=8 through SubPath_type=255 are reserved.

In SubPath_type shown in FIG. 45, new types, i.e., SubPath_type=5, 6,and 7 can be used. In SubPath_type=7, the main TS referred to by theplay item, i.e., the main clip AV stream, includes a sub TS referred toby a sub-path. Accordingly, instead of stream_entry( ) discussed withreference to FIG. 15, the second stream_entry( ) shown in FIG. 46 inwhich type=3 is defined.

Type=3 defined in the second stream_entry( ) is used for identifying anelementary stream referred to by a sub-path and contained in the mainclip when SubPath_type=7.

In FIG. 46, portions similar to those in FIG. 15 are not explained.

When type=3, a sub-path refers to the same clip as that referred by themain path, in other words, a plurality of elementary streams aremultiplexed into the main clip, and both the main path and sub-pathrefer to one of the elementary streams. In this case, whenSubPath_type=7, for specifying the elementary stream referred to by thesub-path from the plurality of elementary streams multiplexed into themain clip, the PID of the main clip is designated byref_to_stream_PID_of_MainClip. Then, SubPath_id is specified byref_to_SubPath_id, and the sub-path defined in PlayList( ) shown in FIG.9 is specified by SubPath_id. The corresponding sub-play item (FIG. 10)is called from the sub-path so that the playback time of the elementarystream (IN_time and OUT_time) can be specified (FIG. 12).

As discussed above, by using the three types (type 1 through type 3),when a play item and at least one sub-path played back in associationwith the play item are provided, one elementary stream can be specifiedfrom the clip referred to by the play item even when the clip is alsoreferred to by the sub-path.

By using SubPath_type shown in FIG. 45, i.e., by using SubPath_type 5,6, and 7 in addition to SubPath_type=1 through 4, which are contained inthe SubPath_type in FIG. 11, a simple playlist, such as that shown inFIG. 47, can be created and used instead of a complicated playlist, suchas that shown in FIG. 44, to implement the picture-in-picture technique(see FIG. 39).

In the example in FIG. 47, a video stream and an audio stream containedin the clip AV stream-0 referred to by play item 1 (PlayItem 1)contained in the main path are used as the primary video stream and theprimary audio stream, respectively. In the example in FIG. 39, the videostream and the audio stream contained in the clip AV stream-0 correspondto the primary video stream 311 and the primary audio stream 312,respectively. The primary video stream 311 is played back in the mainscreen 301, and at the same time, the primary audio stream 312 is playedback (output).

As in the example in FIG. 44, in the example in FIG. 47, the secondaryvideo stream and the secondary audio stream that are played backsimultaneously with the primary video stream in the clip AV stream-0 arecontained in the same clip AV stream-1.

In the example in FIG. 47, as the sub-path A(subPath-A) type,SubPath_type=5 is used, and more specifically, the main-path-TSnon-multiplexed type and AV synchronized type of the picture-in-picturepresentation path is used. Accordingly, the sub-play item referred to bythe sub-path A(SubPath-A) can refer to the secondary video stream andthe secondary audio stream contained in the clip AV stream-1 at the sametime. In the example in FIG. 39, the secondary video stream and thesecondary audio stream contained in the clip AV stream-1 referred to bythe only sub-path A(SubPath-A) correspond to the secondary video stream313 and the secondary audio stream 314, respectively. Then, thesecondary video stream 313 is played back in the sub-screen 302, and atthe same time, the secondary audio stream 314 is played back (output).

In this case, if SubPath_type=5 is used as the sub-path A(SubPath-A),the secondary video stream 313 and the secondary audio stream 314 areplayed back in synchronization with the primary video stream 311.

In other words, if it is desired or necessary that the secondary videostream 313 and the secondary audio stream 314 be played backasynchronously with the primary video stream 311, SubPath_type=6, i.e.,the main-path-TS non-multiplexed and AV non-synchronized type of apicture-in-picture presentation path (including at least one ES), isselected as the sub-path A(SubPath-A).

As discussed above, by using SubPath_type in FIG. 45, thepicture-in-picture technique can be implemented by using only the mainpath and one sub-path.

More specifically, to implement the picture-in-picture technique inwhich the secondary video stream and the secondary audio streamcontained in the same clip AV stream-1 are used as the secondary videostream 313 and the secondary audio stream 314, respectively, thesecondary video stream 313 and the secondary audio stream 314 arereferred to by two different sub-paths in the playlist shown in FIG. 44generated by using SubPath_type shown in FIG. 11. In contrast, accordingto the playlist shown in FIG. 47 generated by using SubPath_type shownin FIG. 45, the secondary video stream and the secondary audio streamcontained in the same clip AV stream-1 can be referred to by onesub-path.

As a result, the secondary video stream and the secondary audio streamcan share the same information, such as SubPlayItem-IN_time andSubPlayItem_OUT_time.

Additionally, upon comparing the playlist in FIG. 47 with that in FIG.44, it is seen that the structure of the playlist can be simplified.

By using SubPath_type=7 in FIG. 45, i.e., the main-path-TS multiplexedtype and AV synchronized type of a picture-in-picture presentation path(including at least one ES), a playlist shown in FIG. 48 can begenerated. As a result, the picture-in-picture technique using theplaylist shown in FIG. 48 can be easily implemented.

In the playlist in FIG. 48, the clip AV stream-0 (which is differentfrom the clip AV stream-0 shown in FIG. 47) is contained in the main TSreferred to by play item 1 (PlayItem1) contained in the main path. Theclip AV stream file-0 includes the main stream referred to by play item1 and a sub-stream referred to by a sub-play item (SPI). The videostream and the audio stream contained in the main stream are used as theprimary video stream and the primary audio stream, respectively. In theexample in FIG. 39, the video stream and the audio stream of the mainstream contained in the clip AV stream file-0 correspond to the primaryvideo stream 311 and the primary audio stream 312, respectively. Theprimary video stream 311 is played back in the main screen 301, and atthe same time, the primary audio stream 312 is played back (output).

In the playlist shown in FIG. 48, the secondary video stream and thesecondary audio stream that are played back simultaneously with theprimary video stream of the main stream are the secondary video streamand the secondary audio stream, respectively, contained in the clip AVstream-0 in the same main TS.

In this case, to create the playlist shown in FIG. 48, SubPath_type=7 isused as the type of sub-path A(SubPath-A). Accordingly, two ESs, such asthe secondary video stream and the secondary audio stream, contained inthe clip AV stream-0 of the main TS, which are referred to by the mainpath, can also be referred to by the sub-play item of the sub-pathA(SubPath-A). In the example in FIG. 39, the secondary video stream andthe secondary audio stream contained in the clip AV stream-0, which arereferred to by the sub-path A(SubPath-A), correspond to the secondaryvideo stream 313 and the secondary audio stream 314, respectively, andthe secondary video stream 313 can be played back in the sub-screen 302,and at the same time, the secondary audio stream 314 can be played back(output). That is, since one file includes a main path and a sub-path,streams contained in another file can also be played back.

In FIG. 48, as sub-paths associated with play item 1, in addition to thesub-path A(SubPath-A), sub-path B(SubPath-B) referring to the clip AVstream-1 (different from clip AV stream-1 shown in FIG. 44) contained ina sub-TS different from the main TS including the clip AV stream-0 isdefined. As discussed above, the playback apparatus can read two TSs(clips) at the same time. Accordingly, the playback apparatus can read,for example, PG contained in the sub-stream together with the primaryvideo, primary audio, secondary video, or secondary audio contained inthe main stream.

Examples of the syntaxes necessary to implement the picture-in-picturetechnique (FIG. 39), i.e., the fifth STN_table( ) shown in FIGS. 40 and41 and SubPath_type in FIG. 45, have been discussed.

To implement the picture-in-picture technique, a playback apparatushaving a function of playing back a primary video stream and a secondaryvideo stream simultaneously, for example, the playback apparatus shownin FIG. 49, is necessary.

Another example of the playback apparatus according to an embodiment ofthe present invention is described below. The playback apparatus 401shown in FIG. 49 is basically similar to the playback apparatus 20 shownin FIG. 25.

The playback apparatus 401 shown in FIG. 49 can perform a playbackoperation in accordance with a playlist including the above-describedmain-path and sub-paths and implementing the picture-in-picturetechnique, for example, the playlist shown in FIG. 47 or 48.

In FIG. 49, elements corresponding to those in FIG. 25 are designated bylike reference numerals, and an explanation thereof is thus omitted.

The playback apparatus 401 shown in FIG. 49 is provided with the storagedrive 31, the switch 32, and the controller 34 having functions andconfigurations similar to those of the playback apparatus 20 shown inFIG. 25. However, the controller 34 has additional functions. Details ofthe additional functions are given below. The playback apparatus 401 isalso provided with the AV decoder 403 having functions andconfigurations slightly different from those of the AV decoder 33.

The elements forming the AV decoder 403 are substantially similar tothose of the AV decoder 33 shown in FIG. 25, except that the first videodecoder 72 substitutes the video decoder 72 of the AV decoder 33, thefirst video plane generator 92 substitutes the video plane generator 92,and the number of output terminals of the PID filter 56 is greater thanthat of the PID filter 56 of the AV decoder 33 by one. Additionally, theAV decoder 403 is provided with a PID filter 411, a second video decoder412, a second video plane generator 413, and a preload buffer 414, whichare not provided for the AV decoder 33.

More specifically, to implement the picture-in-picture technique, it isnecessary to decode primary video streams and secondary video streams.The first video decoder 72 and the second video decoder 412 havingfunctions and configurations similar to each other decode the primaryvideo streams and the secondary video streams, respectively. The firstvideo plane generator 92 and the second video plane generator 413 havingfunctions and configurations similar to each other are provided inassociation with the first video decoder 72 and the second video decoder412, respectively.

The PID filter 411 receives video streams of main clip AV streams orvideo streams of sub-clip AV streams from the PID filter 55 or the PIDfilter 56, respectively. Then, the PID filter 411 allocates the inputvideo streams to the first video decoder 72 or the second video decoder412 according to the PIDs. More specifically, if primary video streamsare supplied, the PID filter 411 supplies them to the first videodecoder 72. If secondary video streams are supplied, the PID filter 411supplies them to the secondary video decoder 412.

In this embodiment, only video streams in the main clip AV stream areused as primary video streams, and video streams in sub-clip AV streamsare not used as primary video streams. However, by considering the useof video streams in sub-clip AV streams as primary video streams in thefuture, the PID filter 411 is configured such that video streams insub-clip AV streams from the PID filter 56 can also be supplied to thefirst video decoder 72.

The preload buffer 414 temporarily stores interactive graphics streamssupplied from the interactive graphics decoder 74. As described above,in this embodiment, a restriction is imposed on the playback apparatus401 such that it can read only two TSs (clips) at the same time.Accordingly, the playback apparatus 401 has the function of obtaininginteractive graphics streams in advance (preloading them) to play backpreloaded interactive graphics streams simultaneously with otherstreams. To implement this function, the preload buffer 414 is disposedfor storing preloaded interactive graphics streams until they can beplayed back with video streams or audio streams.

An example of processing performed by the playback apparatus 401 shownin FIG. 49 according to the picture-in-picture technique, and morespecifically, processing for switching secondary video streams to beplayed back while a primary video stream is being played back(hereinafter simply referred to as the “secondary video switchingprocessing”) is described below with reference to the flowchart in FIGS.50 and 51.

In step S101 in FIG. 50, the controller 34 obtains an order list ofsecondary video stream numbers (may be IDs) and a list of primary audiostreams, secondary audio streams, and subtitle streams that can becombined with secondary video streams from the fifth STN_table( ) shownin FIGS. 40 and 41.

It is now assumed that, after step S101, a stream number table, such asthat shown in FIG. 42, is generated based on the obtained list, and thestream number table or a predetermined graphical user interface (GUI)image generated based on the stream number table is presented to theuser. The process then proceeds to step S102.

In step S102, the controller 34 receives an instruction to switchsecondary video streams from the user.

More specifically, in step S102, the switching operation performed bythe user discussed with reference to FIGS. 42 and 43 is received by thecontroller 34 as an instruction to switch secondary video streams.

In step S103, the controller 34 obtains a combination number subsequentto the current combination number of a secondary video stream, a primaryaudio stream, a secondary audio stream, and a subtitle stream.

More specifically, if the stream number table shown in FIG. 42 ispresented to the user, there are three combinations, i.e., the firstcombination through third combination, of a secondary video stream, aprimary audio stream, a secondary audio stream, and a subtitle stream.The first combination is a combination of video 2, audio 2, audio 4, andsub-picture 3. The second combination is a combination of video 1, audio1, audio 4, and sub-picture 1. The third combination is a combination ofvideo 1, audio 1, audio 5, and sub-picture 1. It is now assumed that 1,2-1, and 2-2 are assigned to the first, second, and third combinations,respectively, as combination numbers. It is also assumed that aninstruction to select the second combination shown in FIG. 43 isreceived by the controller 34. In this case, in step S103, thecontroller 34 obtains 2-1 as the subsequent combination number.

In step S104, the controller 34 then determines by referring tostream_attribute( ) whether it has a function of playing back aplurality of streams associated with the obtained number (in this case,the number obtained in step S103).

More specifically, since an instruction to select the second combinationis received by the controller 34 in step S103, the controller 34determines in step S104 whether it has a function of playing back audio1 and audio 4.

A specific example of a determination as to whether the function ofplaying back audio streams has been discussed in the description of stepS74 in FIG. 30, and thus, an explanation thereof is omitted here.

In step S104, a determination as to whether the function of playing backother types of streams, such as video streams, may also be made.

If it is determined in step S104 that the function of playing back aplurality of streams associated with the obtained number is notprovided, the process proceeds to step S105. In step S105, thecontroller 34 obtains the subsequent combination number. That is, thecurrent combination number is skipped and is not played back. Theprocess then returns to step S104, and steps S104 and S105 are repeated.That is, steps S104 and S105 are repeated until a combination numberhaving audio streams that can be played back by the playback apparatus401 is obtained.

If it is determined in step S104 that the function of playing back aplurality of streams associated with the obtained number (numberobtained in step S103 or S105) is provided, the process proceeds to.step S106.

In step S106, the controller 34 checks, based on the type ofstream_entry( ), clips containing the secondary video stream, primaryaudio stream, secondary audio stream, and subtitle stream associatedwith the obtained number. That is, the controller 34 checks whether eachof the secondary video stream, primary audio stream, secondary audiostream, and subtitle stream is contained in the main clip or a sub-clip.A specific example of step S106 has been discussed in the description ofstep S76 in FIG. 30, and thus, an explanation thereof is omitted here.

In step S107, the controller 34 specifies the desired secondary videostream, primary audio stream, secondary audio stream, and subtitlestream. That is, in step S107, the desired streams associated with theobtained number in the main clip or a sub-clip are specified. A specificexample of step S107 has been discussed in the description of step S77in FIG. 30, and thus, an explanation thereof is omitted here.

In step S108, the controller 34 instructs the storage drive 31 to readthe specified secondary video stream, primary audio stream, secondaryaudio stream, and subtitle stream from the clips containing thosestreams. In response to this instruction, the storage drive 31 reads thespecified streams from the target clip. More specifically, in step S108,the controller 34 instructs the storage drive 31 to read the streamsspecified in step S107 from the clip specified in step S106.

Then, in step S109, the controller 34 instructs the AV decoder 403 toplay back the read streams. More specifically, the controller 34instructs the second video decoder 412 to decode the secondary videostream, the first audio decoder 75-1 to decode the primary audio stream,the second audio decoder 75-2 to decode the secondary audio stream, andthe presentation graphics decoder 73 to decode the subtitle stream.

In step S110, the AV decoder 403 decodes the secondary video stream,primary audio stream, secondary audio stream, and subtitle stream andoutputs the decoded streams. The processing is then completed.

In this case, as stated above, for the primary audio stream and thesecondary audio stream, an audio signal generated by mixing and playingback the primary audio stream and the secondary audio stream is output,as discussed in the description of step S80 in FIG. 30.

As a result of the secondary video switching processing, thepicture-in-picture technique discussed with reference to FIG. 39 isimplemented. More specifically, in FIG. 39, while video corresponding tothe primary video stream 311 is being displayed in the main screen 301,video corresponding to the secondary video stream 313 output in stepS110 is displayed in the sub-screen 302, subtitles corresponding to thesubtitle stream 315 output in step S110 are displayed at a predeterminedposition of the main screen 301, and sound generated by mixing theprimary audio stream 313 and the secondary audio stream 314 is outputfrom a speaker (not shown).

As discussed above, by using the fifth STN_table( ) shown in FIGS. 40and 41, the picture-in-picture technique can be implemented.

To perform the picture-in-picture technique, it is possible that theplaylist (FIG. 44) generated by using SubPath_type shown in FIG. 11 beused. As stated above, by using such a playlist, however, a secondaryvideo stream and a secondary audio stream contained in the same clip AVstream are referred to by different sub-paths, i.e., they are defined asdifferent sub-play items. As a result, the structure of the playlistbecomes complicated, as described above.

To solve this problem, as stated above, SubPath_type, such asSubPath_type shown in FIG. 45, can be used so that two or moreelementary streams in the same clip AV stream can be referred to by onesub-path, i.e., two or more ESs in the same clip AV stream can bedefined as one sub-play item.

From the viewpoint of the creators of a playlist, however, even thoughthe structure of the playlist becomes simple by using SubPath_type shownin FIG. 45, the creator still has to determine which combinations ofstreams are possible and which combinations of streams are not possible,i.e., to determine which sub-paths are included, to implement thepicture-in-picture technique. Accordingly, there is still a demand forsimply creating a playlist.

To respond to such a demand, in an embodiment of the present invention,sub-paths that can be included in a playlist are restricted bySubPath_type shown in FIG. 45 depending on the type of playlist. Such atechnique is referred to as the “sub-path restriction technique”.

According to the sub-path restriction technique, the sub-paths that canbe included in a playlist are restricted, which enables the user todetermine which sub-paths are included in the playlist, therebyfacilitating the creation of the playlist.

Details of the sub-path restriction technique are given below.

In the sub-path restriction technique, the type of restriction variesdepending on the number of TSs that can be read at the same time by theplayback apparatus. In this embodiment, as stated above, the number ofTSs that can be read simultaneously is two. Accordingly, the sub-pathrestriction technique when the number of TSs that can be readsimultaneously is two is described below.

In this embodiment, the playlist can be largely divided into two types,i.e., browsable slideshow (non-synchronized) and movie-type/time-basedslideshow (synchronized). The type of playlist can be determined byapplication_type contained in clip_Information type of the clip referredto by the playlist.

The application_type is indicated in ClipInfo( ) in a clip informationfile of a clip. For the sake of simple description, however, the syntaxof ClipInfo( ) is not mentioned here, and only application_typeindicated in ClipInfo( ) is discussed below with reference to FIG. 52.

In FIG. 52, application_type=0 is reserved. The application_type=1 isused for main TSs for movie applications. The main TS is a transportstream as a play item referred to by the main path in the playlist. Theapplication_type=2 is used for main TSs for time-based slideshow, i.e.,main TSs for still image slideshow. The application_type=3 is used forTSs for browsable slideshow, i.e., TSs for video slideshow.

The application_type=4 is used for sub-path TSs for browsable slideshow,which is indicated in ClipInfo( ) for, for example, clip AV streamscontaining BGM that is played back asynchronously withapplication_type=3. The application_type=5 is used for sub-path TSs forinteractive graphics. The application_type=6 is used for sub-path TSsfor text subtitles. The application_type=7 is used for sub-path TSsincluding at least one ES. The application_type=8 throughapplication_type=255 are reserved.

In this embodiment, when application_type=3 in application typeindicated in ClipInfo( ) of a main TS referred to by a playlist, theplaylist is classified into browsable slideshow (non-synchronized type).When playlist=1 or 2 in application_type indicated in ClipInfo( ), theplaylist is classified into movie-type/time-based slideshow(synchronized).

In this case, sub-paths that can be provided for playlists arerestricted to sub-paths shown in FIG. 57 depending on the types ofplaylists (non-synchronized or synchronized). Such a restriction isimposed by the sub-path restriction technique.

The number of sub-paths indicated in the right side of FIG. 53designates the number of sub-paths whose type is indicated inSubPath_type provided for the main TS.

The numbers indicated in SubPath_type correspond to the numbersindicated in SubPath_type shown in FIG. 45.

When the type of playlist is non-synchronized type, as shown in FIG. 53,i.e., when the type of playlist is browsable slideshow havingapplication_type=3, only (1) at least 0 sub-paths of SubPath_type=2 or(2) at least 0 sub-paths of SubPath_type=3 are allowed. In other words,sub-paths other than the above-described (1) and (2) sub-paths areprohibited.

In (2) sub-path, if the main TS of application_type=3 contains aninteractive graphics stream (IG), such sub-paths are prohibited (see *2in FIG. 53). The reason is as follows.

From the viewpoint of IGs, playlists including IGs are largely dividedinto a first type and a second type. In the first type of playlist, anIG is multiplexed into the main TS, and the IG is played backsimultaneously with an audio or video stream contained in the main TS.In the second type of playlist, an IG is included in a sub-path havingSubPath_type=3, and the IG is preloaded (which is used for a popupmenu). To play back the second type of playlist, the preload buffer 414is disposed in the playback apparatus 401 shown in FIG. 49, as describedabove.

Since only one IG decoder is provided for the playback apparatus of thisembodiment, and more specifically, since the single IG decoder 74 isprovided for the playback apparatus 401, the following restriction isimposed. In the first type of playlist, while the IG in the main TS isbeing decoded by the IG decoder, another IG cannot be preloaded. In thesecond type of playlist, while a first IG, which is preloaded, is inputinto the IG decoder, a second IG from another main TS cannot be inputinto the IG decoder.

Because of the above-described reason, a restriction is imposed suchthat a playlist including STN_table( ) referring to an IG multiplexedinto a main TS is not allowed to have a sub-path having SubPath_type=3.Under this restriction, if an IG is contained in the main TS ofapplication_type=3, such sub-paths are prohibited (see *2 in FIG. 53).

When the type of playlist is synchronized type, i.e., i.e., when thetype of playlist is movie-type/time-based slideshow ofapplication_type=1 or 2, only (3) at least 0 sub-paths ofSubPath_type=3, (4) at least 0 sub-paths of SubPath_type=4 (5) at least0 sub-paths of SubPath_type=5, (6) at least 0 sub-paths ofSubPath_type=6, or (7) 0 or 1 sub-path of SubPath_type=7 are allowed. Inother words, sub-paths of SubPath_type=2 are prohibited.

In (3) sub-path, if the main TS of application_type=3 contains an IG, orif the TS referred to by a sub-path of SubPath_type=5 contains an IG,such sub-paths are prohibited (see *1 in FIG. 53). This is also becauseof the above-described restriction.

Additionally, in this embodiment, as stated above, the number of clipsthat can be referred to at the same time by a playlist, i.e., the numberof TSs that can be read at the same time by the playback apparatus, istwo. Accordingly, to ensure that ESs that can be referred to at the sametime by the same playlist are contained in at most two clips, i.e., thatESs that can be played back at the same time are referred to by at mosttwo clip AV stream files, a restriction is imposed by the sub-pathrestriction technique such that the following conditions are satisfied.

The condition, which is imposed by the sub-path restriction technique,for combining primary_video_stream, primary_audio_stream,PG_textST_stream other than text subtitle streams, IG_stream other thanIGs for popup menu, secondary_video_stream, and secondary_audio_streamreferred to by STN_table( ) is as follows.

In an ES specified by primary_video_stream_number, an ES specified byprimary_audio_stream_number, an ES specified by PG_textST_stream_number,an ES specified by IG_stream_number, an ES specified bysecondary_video_stream_number, and an ES specified bysecondary_audio_stream_number, combinations of streams that can beplayed back simultaneously should be stored in at most two clip AVstream files. The excluded text subtitle streams or IGs for pop-up menuare preloaded streams. Accordingly, they are not simultaneously readfrom an optical disc or a hard disk though they are played back(displayed) together, and thus, they may be stored in a clip AV streamfile different from the above-described two clip AV stream files.

ESs referred to by STN_table( ) may be stored by three or more clip AVstream files, but ESs that can be played back simultaneously should bestored in at most two of those clip AV stream files.

The sub-path restriction technique also imposes the restriction suchthat it is necessary that the combination of the number of play itemsand the number of sub-paths is one of the following combinations (a),(b), and (c). The combination (a) is only one play item (the topmost rowin FIG. 54), the combination (b) is one play item and one sub-path (themiddle row in FIG. 54), and the combination (c) is one play item, onesub-path, and one sub-path=7, i.e., one play item and two sub-paths (oneof the sub-paths should be SubPath_type=7) (the bottommost row in FIG.54).

In one type of sub-path restriction technique, the types of sub-paths(SubPath_type) that can be created according to the types of playlistsare restricted.

In other words, the sub-path restriction technique includes conditions,such as the type of playlist (in the above-described example, typerepresented by application_type of the main TS), the number of TSs thatcan be read at the same time by the playback apparatus (in theabove-described example, two), and whether an IG to be preloaded iscontained in an ES referred to by a sub-path of the playlist) (in thisexample, whether the sub-path is SubPath_type=3). To satisfy thoseconditions, the sub-paths to be included in the playlist are determined,and as a result, a playlist including those sub-paths is created.

Specific examples of playlists created by the sub-path restrictiontechnique are given below with reference to FIGS. 55 through 58.

FIG. 55 illustrates a playlist of browsable slideshow (non-synchronizedtype) which does not have SubPath_type=3, i.e., a playlist includingsub-path 1 through sub-path 3 of SubPath_type=2. SubPath_type=3 is notcontained in the playlist because an IG is contained in the clip AVstream-0 (i.e., main TS) referred to by play item 1 and play item 2.Since the playlist in this example is browsable slideshow whichsequentially displays a plurality of still images by the user, videostreams contained in the clip AV stream-0 store still image data.

The playlist shown in FIG. 55 is created by using the conditions thatonly (1) at least 0 sub-paths of SubPath_type=2 or (2) at least 0sub-paths of SubPath_type=3 are allowed and sub-paths other than (1) or(2) sub-paths are prohibited, and that sub-paths of SubPath_type=3 areprohibited if an IG is contained in the main TS of application_type=3(see *2 in FIG. 53).

In contrast to the example in FIG. 55, FIG. 56 illustrates a playlist ofbrowsable slideshow (non-synchronized type) which have SubPath_type=3,i.e., a playlist including sub-path 1 and sub-path 2 of SubPath=type2and sub-path 3 of SubPath_type=3. SubPath_type=3 is contained in theplaylist because an IG is not contained in the clip AV stream-0 referredto by play item 1 and play item 2, and SubPath_type=3 is used forreferring to an IG contained in a clip AV stream-3, which is differentfrom the clip AV stream-0.

The conditions used for creating the playlist shown in FIG. 56 are thesame as those for the playlist shown in FIG. 55.

In other words, an example of the playlist on which the restrictionindicated by *2 in FIG. 53, i.e., in “(2) sub-path, if the main TS ofapplication_type=3 contains an IG, such sub-paths of SubPath_type=3 areprohibited”, has to be imposed is the example in FIG. 55, and an exampleof the playlist on which such a restriction does not have to be imposedis the example in FIG. 56.

As described above, FIGS. 55 and 56 illustrate examples of playlists ofbrowsable slideshow (non-synchronized type). In contrast, FIGS. 57 and58 illustrate examples of playlists of movie-type/time-based slideshow(synchronized type).

More specifically, FIG. 57 illustrates a playlist of synchronized typein which a secondary video stream and a secondary audio stream are notmultiplexed into the main TS (i.e., clip AV stream-0), i.e., theplaylist including sub-path 1 and sub-path 2 of SubPath_type=5.

By using the condition that (6) “at least 0 sub-paths of SubPath_type=6is allowed” described in FIG. 53, the playlist shown in FIG. 57 iscreated.

FIG. 58 illustrates a playlist of synchronized type in which the mainTS, i.e., the clip AV stream-0, referred to by the playlist contains amain stream and a sub-stream and a secondary video stream and asecondary audio stream are multiplexed into the clip AV stream-0 formingthe main TS. Accordingly, the playlist includes sub-path 1 ofSubPath_type=7 and sub-2 and sub-path 3 of SubPath_type=5.

By using conditions that (5) “at least 0 sub-paths of SubPath_type=5 areallowed”, and (7) “0 sub-path and one sub-path of SubPath_type=7 areallowed”, the playlist shown in FIG. 58 are created.

The playlists created by the above-described sub-path restrictiontechnique can also be played back by the playback apparatus 401 shown inFIG. 49.

For example, the playback apparatus 401 plays back a playlist ofnon-synchronized type, i.e., a playlist of browsable slideshow havingapplication_type=3, in the following manner. If the playlist refers toat least one sub-path of SubPath_type=3 (interactive graphicspresentation menu), the playback apparatus 401 preloads a clip AV streamof SubPath_type=3, i.e., an interactive graphics stream, in the preloadbuffer 414 before playing back the playlist. If the playlist refers toat least one sub-path of SubPath_type=2, the playback apparatus 401refers to a predetermined sub-path (SubPath_type=2) and plays it backsince sub-paths can be referred to only one by one (the number of TSsthat can be read at the same time is two, and one of them is the main TSreferred to by the main TS).

The interactive graphics presentation menu includes two menus, i.e., apopup menu that can be displayed or erased by the ON/OFF operation ofthe user, and an always-on menu that is always displayed. Details ofplayback processing for a playlist of application_type=3 are given belowwith reference to the flowcharts in FIGS. 59 and 60.

The playback apparatus 401 plays back a playlist of synchronized type,i.e., a playlist of movie-type/time-based slideshow of clips havingapplication_type=1 or 2, in the following manner. If the playlist refersto at least one sub-path of SubPath_type=3 or 4 (interactive graphicsstream or text subtitle stream), the playback apparatus 401 preloads aclip AV stream, i.e., an interactive graphics stream or a text subtitlestream, of SubPath_type=3 or 4 in the preload buffer 414 or the buffer54 before playing it back. If the playlist refers to at least onesub-path of SubPath_type=5 or 6, the playback apparatus 401 refers to apredetermined sub-path (SubPath_type=5 or 6) and plays it back sincesub-paths can be referred to only one by one (the number of TSs that canbe read at the same time is two, and one of them is the main TS referredto by the main TS). However, if the sub-paths contained in the playlistincludes at least one sub-path of SubPath_type=7, the playback apparatus401 can refer to one sub-path of SubPath_type=7 and plays it back whileplaying back one sub-path of SubPath_type=5 or 6 since the sub-path ofSubPath_type=7 refers to an ES contained in the main TS.

Details of playback processing for a playlist of application_type=1 or 2are given below with reference to FIGS. 61 through 64.

An example of playback processing for a playlist of application_type=3is described below with reference to FIGS. 59 and 60.

The controller 34 shown in FIG. 49 checks application_type of the mainTS referred to by the main path of the playlist, and if it is found tobe application_type=3, the controller 34 starts the playback processingfor the playlist of application_type=3.

In step S121, the controller 34 determines whether the main TS includesan interactive graphics stream (IG).

If it is determined in step S121 the main TS does not include an IG, theprocess proceeds to step S126.

If it is determined in step S121 that the main TS includes an IG, theprocess proceeds to step S122 to determine whether there is any sub-pathof SubPath_type=3.

If it is determined in step S122 that there is no sub-path ofSubPath_type=3, the process proceeds to step S126.

If it is determined in step S122 that there is a sub-path ofSubPath_type=3, the process proceeds to step S123. In step S123, thecontroller 34 checks the clip referred to by the selected sub-path ofSubPath_type=3.

The controller 34 then instructs the storage drive 31 to read the streamspecified by the sub-path, i.e., the IG, from the clip. The storagedrive 31 reads the IG in response to this instruction. Then, thecontroller 34 instructs the interactive graphics decoder 74 to decodethe IG.

Then, in step S124, the interactive graphics decoder 74 decodes the IG.Then, in step S125, the interactive graphics decoder 74 stores thedecoded IG in the preload buffer 414.

After step S125, or if the outcome of step S121 or S122 is NO, theprocess proceeds to step S126 to determine whether there is any sub-pathof SubPath_type=2.

If it is determined in step S126 that there is no sub-path ofSubPath_type=2, the process proceeds to step S129.

If it is determined in step S126 that there is a sub-path ofSubPath_type=2, the process proceeds to step S127. In step S127, thecontroller 34 checks the clip referred to by the selected sub-path(SubPath_type=2).

Then, the controller 34 instructs the storage drive 31 to read thestream specified by the sub-path, i.e., an audio stream, from the clip.The storage drive 31 reads the audio stream in response to thisinstruction. The controller 34 then instructs the second audio decoder75-2 to decode the read audio stream.

Then, in step S128, the second audio decoder 75-2 decodes the read audiostream.

After step S128 or if the outcome of step S126 is NO, the processproceeds to step S129.

In step S129, the AV decoder 403 decodes the main clip AV stream. Themain clip AV stream includes a video stream or an audio stream referredto by the main path of the playlist to be played back, for example,primary video streams and audio streams in the picture-in-picturetechnique. The first video decoder 72 or the first audio decoder 75-1executes step S129.

In step S130, the AV decoder 403 combines the decoded main clip AVstream with the decoded sub-path stream, and outputs the combinedstream. The decoded sub-path stream is the IG decoded in step S124 andstored in the preload buffer 414 in step S125 or the audio streamdecoded in step S128.

In step S131, the controller 34 determines whether an instruction toswitch sub-paths of SubPath_type=2 has been given while outputting thestream combined in step S130.

If it is determined in step S131 that an instruction to switch sub-pathsof SubPath_type=2 has been given, the process returns to step S127. Thatis, the audio stream to be combined with the main clip AV stream isswitched.

If it is determined in step S131 that an instruction to switch sub-pathsof SubPath_type=2 has not been given, the playback processing iscompleted.

An example of playback processing for a playlist including a clip ofapplication_type=1 or 2 is described below with reference to theflowcharts in FIGS. 61 through 64.

The controller 34 shown in FIG. 49 checks application_type of the mainTS referred to by the main path of a playlist to be played back, and ifit is found to be application_type=1 or 2, the controller 34 startsplayback processing for the playlist.

In step S141, the controller 34 determines whether the main TS includesan IG.

If it is determined in step S141 that the main TS does not include anIG, the process proceeds to step S146.

If it is determined in step S141 that the main TS includes an IG, theprocess proceeds to step S142 to determine whether there is any sub-pathof SubPath_type=3.

If it is determined in step S142 that there is no sub-path ofSubPath_type=3, the process proceeds to step S146.

If it is determined in step S142 that there is a sub-path ofSubPath_type=3, the process proceeds to step S143. In step S143, thecontroller 34 checks the clip referred to by the selected sub-path(SubPath_type=3).

The controller 34 then instructs the storage drive 31 to read the streamspecified by the sub-path, i.e., the IG, from the clip. The storagedrive 31 reads the IG in response to this instruction. The controller 34then instructs the interactive graphics decoder 74 to decode the readIG.

Then, in step S144, the interactive graphics decoder 74 decodes the readIG. Then, in step S145, the interactive decoder 74 stores the decoded IGin the preload buffer 414.

After step S145, or if the outcome of step S141 or S142 is NO, theprocess proceeds to step S146 to determine whether there is any sub-pathof SubPath_type=4.

If it is determined in step S146 that there is no sub-path ofSubPath_type=4, the process proceeds to step S149.

If it is determined in step S146 that there is a sub-path ofSubPath_type=4, the process proceeds to step S147. In step S147, thecontroller checks the clip referred to by the selected sub-path(SubPath_type=4).

The controller 34 then instructs the storage drive 31 to read the streamspecified by the sub-path, i.e., the text subtitle stream. The storagedrive 31 reads the text subtitle stream in response to this instruction.The controller 34 then instructs the text-ST composition 76 to decodethe read text subtitle stream.

In step S148, the text-ST composition 76 decodes the read text subtitle.

After step S148, or if the outcome of step S146 is NO, the processproceeds to step S149 to determine whether there is any sub-path ofSubPath_type=7.

If it is determined in step S149 that there is no sub-path ofSubPath_type=7, the process proceeds to step S152.

If it is determined in step S149 that there is a sub-path ofSubPath_type=7, the process proceeds to step S150. In step S150, thecontroller 34 checks the clip referred to by the selected sub-path(SubPath_type=7).

The controller 34 then instructs the storage drive 31 to read the streamspecified by the sub-path, i.e., the video/audio stream, from the clip.The storage drive 31 reads the video/audio stream in response to thisinstruction. Then, the controller 34 instructs the second video decoder412 or the second audio decoder 75-2 to decode the read video/audiostream.

In step S151, the second video decoder 412 or the second audio decoder75-2 decodes the read video/audio stream.

After step S151, or if the outcome of step S149 is NO, the processproceeds to step S152 to determine whether there is any sub-path ofSubPath_type=5.

If it is determined in step S152 that there is no sub-path ofSubPath_type=5, the process proceeds to step S156.

If it is determined in step S152 that there is a sub-path ofSubPath_type=5, the process proceeds to step S153. In step S153, thecontroller 34 checks the clip referred to by the selected sub-path(SubPath_type=5).

Then, the controller 34 determines by referring to stream_attributes( )in step S154 whether it has the function of playing back the audiostream contained in the clip. A specific example of a determination asto whether the function of playing back audio streams has been discussedin the description of step S74 in FIG. 30, and thus, an explanationthereof is omitted here.

If it is determined in step S154 that the function of playing back theaudio stream is not provided, the process proceeds to step S156.

If it is determined in step S154 that the function of playing back theaudio stream is provided, the controller 34 instructs the storage drive31 to read the stream specified by the sub-path, i.e., the audio stream,from the clip. The storage drive 31 reads the audio stream in responseto this instruction. The controller 34 then instructs the second audiodecoder 75-2 to decode the read audio stream.

Then, in step S155, the second audio decoder 75-2 decodes the read audiostream.

After step S155, or if the outcome of step S152 or S154 is NO, theprocess proceeds to step S156 to determine whether there is any sub-pathof SubPath_type=6.

If it is determined in step S156 that there is no sub-path ofSubPath_type=6, the process proceeds to step S161.

If it is determined in step S156 that there is a sub-path ofSubPath_type=6, the process proceeds to step S157. In step S157, thecontroller 34 checks the clip referred to by the selected sub-path(SubPath_type=6).

In step S158, the controller 34 determines by referring tostream_attributes whether it has the function of playing back the audiostream contained in the clip. A specific example of a determination asto whether the function of playing back audio streams has been discussedin the description of step S74 in FIG. 30, and thus, an explanationthereof is omitted here.

If it is determined in step S158 that the function of playing back theaudio stream is not provided, the controller 34 instructs the storagedrive 31 to read the corresponding video stream specified by thesub-path from the clip. The storage drive 31 reads the video stream fromthe clip in response to this instruction. In this case, the controller34 prohibits the decoding of audio streams contained in the read clip,and instructs the second video decoder 412 to decode the video stream.Then, the process proceeds to step S160.

If it is determined in step S158 that the function of playing back theaudio stream contained in the clip is provided, the controller 34instructs the storage drive 31 to read the stream specified by thesub-path, i.e., the video stream and the audio stream, from the clip.The storage drive 31 reads the video stream and the audio stream inresponse to this instruction. Then, the controller 34 instructs thesecond audio decoder 75-2 to decode the read audio stream, and thesecond video decoder 412 to decode the read video stream.

Then, in step S159, the second audio decoder 75-2 decodes the read audiostream.

After step S159, or if the outcome of step S158 is NO, the processproceeds to step S160.

In step S160, the second video decoder 412 decodes the read videostream.

After step S160, or if the outcome of step S156 is NO, the processproceeds to step S161.

In step S161, the AV decoder 403 decodes the main clip AV stream. Themain clip AV stream includes a video stream or an audio stream containedin the main TS referred to by the main path of the playlist to be playedback. The main clip AV stream is a primary video stream or a primaryaudio stream in the picture-in-picture technique. That is, the firstvideo decoder 72 or the first audio decoder 75-1 of the AV decoder 403executes step S161.

In step S162, the AV decoder 403 combines the decoded main clip AVstream with the decoded sub-path stream, and outputs the combinedstream. The decoded sub-path stream includes at least 0 sub-path streamamong the IG decoded in step S144 and stored in the preload buffer 414in step S145, the text subtitle decoded in step S148, the audio streamdecoded in step S151, the audio stream decoded in step S155, the audiostream decoded in step S159, and the video stream decoded in step S160.

In step S163, the controller 34 determines whether an instruction toswitch sub-paths has been given by the user operation while outputtingthe stream combined in step S162.

If it is determined in step S163 that there is no instruction to switchsub-paths, the playback processing for a playlist of application_type=1or 2 is completed.

If it is determined in step S163 that an instruction to switch sub-pathshas been given, the process proceeds to step S164.

In step S164, the controller 34 checks SubPath_type of the sub-pathselected by the switching instruction.

In step S165, the controller 34 determines whether the result of stepS164 is SubPath_type=3.

If it is determined in step S165 that SubPath_type=3, the processreturns to step S143. That is, the IG to be combined with the main clipAV stream is switched.

If it is determined in step S165 that the result of step S164 is notSubPath_type=3, the process proceeds to step S166 to determine whetherthe result of step S164 is SubPath_type=4.

If it is determined in step S166 that SubPath_type=4, the processreturns to step S147. That is, the text subtitle to be combined with themain clip AV stream is switched.

If it is determined in step S166 that the result of step S164 is notSubPath_type=4, the process proceeds to step S167 to determine whetherthe result of step S164 is SubPath_type=7.

If it is determined in step S167 that SubPath_type=7, the processreturns to step S150. That is, the video/audio stream to be combinedwith the main clip AV stream is switched.

If it is determined in step S167 that the result of step S164 is notSubPath_type=7, the process proceeds to step S168 to determine whetherthe result of step S164 is SubPath_type=5.

If it is determined in step S168 that SubPath_type=5, the processreturns to step S153. That is, the audio stream to be combined with themain clip AV stream is switched.

If it is determined in step S168 that the result of step S164 is notSubPath_type=5, the process proceeds to step S169 to determine whetherthe result of step S164 is SubPath_type=6.

If it is determined in step S169 that SubPath_type=6, the processreturns to step S157. That is, the audio stream or the video stream tobe combined with the main clip AV stream is switched.

If it is determined in step S169 that the result of step S164 is notSubPath_type=6, the playback processing for a playlist ofapplication_type=1 or 2 is completed.

As has been discussed above, to implement an application using thepicture-in-picture technique, the definition of combinations of streamsto be played back together with a primary video stream, i.e.,combinations of secondary video streams, primary audio streams,secondary audio streams, and subtitle streams, is necessary.

By defining a plurality of combinations, not only a primary video streamor a primary audio stream played back in the main screen 301, but also asecondary video stream, a secondary audio stream, or a subtitle streamplayed back in the sub-screen 302 can be easily switched.

A manufacturing method for the recording medium 21 on which data thatcan be played back by the playback apparatus 20 or 401 is recorded isdiscussed below in the context of a disc-shaped recording medium withreference to FIGS. 65 and 66.

An original board, such as glass, is prepared, as shown in FIG. 65, andthen, a recording material, such as a photoresist, is applied onto theglass, thereby forming a recording original disc.

In a software production processor, as shown in FIG. 66, video datawhich is encoded by a video encoder and which is to be played back bythe playback apparatus 20 or 401 is temporarily stored in a buffer.Audio data encoded by an audio encoder is temporarily stored in abuffer, and also, data other than streams (e.g., indexes, playlists,play items, etc.) encoded by a data encoder is temporarily stored in abuffer. The video data, audio data, and data other than streams storedin the buffers are multiplexed with a synchronizing signal in amultiplexer (MPX), and are provided with error correction codes in anerror-correcting code (ECC) circuit. Then, the multiplexed data ismodulated in a modulation circuit (MOD), and is then recorded on, forexample, magnetic tape, according to a predetermined format. As aresult, software to be recorded on the recording medium 11 and to beplayed back by the playback apparatus 20 or 401 is produced.

The software is edited (subjected to pre-mastering) if necessary so thata signal format to be recorded on an optical disc (recording signal) isgenerated. A laser beam is then modulated in accordance with thisrecording signal, and the modulated laser beam is applied to thephotoresist on the original disc so that the photoresist is exposed tothe laser beam in accordance with the recording signal.

Thereafter, the original disc is developed, and pits appear on theoriginal disc. The original disc is then subjected to treatment, suchas, electroforming, so that a metal original disc having pitstransferred from on the original disc is fabricated. A metal stamper isthen fabricated from the metal original disc. This metal stamper is usedas a metal mold.

A material, such as polymethyl methacrylate (PMMA) or polycarbonate (PC)is injected into this metal stamper and is fixed. Alternatively, afterapplying an ultraviolet curable resin (2P) onto the metal stamper, theresin is irradiated with an ultraviolet and is cured. This makes itpossible to transfer pits on the metal stamper to the resin, therebyforming a replica.

A reflective film is then formed on the replica by deposition,sputtering, or spin-coating.

Then, necessary processing, such as adjusting the inner and outerdiameters of the resulting disc and laminating two discs, is performed.Then, a label and a hug are attached to the disc and the disc is theninserted into a cartridge. As a result, the recording medium 11 on whichdata to be played back by the playback apparatus 20 or 401 is recordedis completed.

The above-described series of processing operations may be executed byhardware or software. In this case, the processing operations can beperformed by a personal computer 500 shown in FIG. 67.

In the personal computer 500, a central processing unit (CPU) 501executes various processing operations according to a program stored ina read only memory (ROM) 502 or a program loaded into a random accessmemory (RAM) 503 from a storage unit 508. In the RAM 503, data necessaryfor the CPU 501 to execute various processing operations is also stored.

The CPU 501, the ROM 502, and the RAM 503 are connected to each othervia an internal bus 504. An input/output interface 505 is also connectedto the internal bus 504.

The input/output interface 505 is connected to an input unit 506, suchas a keyboard and a mouse, an output unit 507, such as a display, forexample, a cathode ray tube (CRT) or a liquid crystal display (LCD), thestorage unit 508, such as a hard disk, and a communication unit 509,such as a modem or a terminal adapter. The communication unit 509performs communication via various networks including telephone lines orcable television.

A drive 510 is connected to the input/output interface 505 if necessary.A removable medium 521, such as a magnetic disk, an optical disc, amagneto-optical disk, or a semiconductor memory, is installed in thedrive 510. A computer program read from the removable medium 521 isinstalled into the storage unit 508.

If software is used for executing the series of processing operations, acorresponding software program is installed from a network or arecording medium.

This recording medium may be formed of a package medium, such as theremovable medium 521, recording the program thereon, which isdistributed to the user separately from the computer. Alternatively, therecording medium may be formed of the ROM 502 or a hard disk forming thestorage unit 508 recording the program thereon, which is distributed tothe user while being built in the computer.

In this specification, steps forming the computer program may beexecuted in chronological order described in this specification.Alternatively, they may be executed in parallel or individually.

The drive 510 can, not only read data recorded on the removable medium521 installed in the drive 510, but also write data onto the removablemedium 521. The personal computer 500 has a function similar to that ofthe software production processor discussed with reference to FIG. 66,for example, the personal computer 500 can execute a program forimplementing a function similar to that of the software productionprocessor by using the CPU 501.

More specifically, the personal computer 500 can generate data similarto data generated by the software production processor discussed withreference to FIG. 66 by using the CPU 501 or can obtain data similar todata generated by an external device, for example, the softwareproduction processor discussed with reference to FIG. 66, via thecommunication unit 509 or the removable medium 521 installed in thedrive 510. The personal computer 500 also serves as a recorder that canrecord the generated or obtained data similar to data generated by thesoftware production processor discussed with reference to FIG. 66 on theremovable medium 521 installed in the drive 510.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

The invention claimed is:
 1. A non-transitory recording medium on whichdata including playback management information to manage playback of atleast two streams including a first stream and a second stream isrecorded, the playback management information comprising: a mainplayback path indicating a position on a time axis of the first stream;a sub playback path indicating a position on the time axis of the secondstream; and type information indicating whether the second stream isplayed back synchronously with the first stream and whether the secondstream is multiplexed into a same file as the first stream, wherein themain playback path includes video data and interactive graphics, andwherein the playback management information satisfies: a first conditionthat a type of the sub playback path corresponds to a set of subplayback path types of a predetermined application media category amonga plurality of application media categories, and a second condition thatthe sub playback path is determined so that a number of files readableat one time does not exceed a predetermined number, and wherein theinclusion of the interactive graphics in the main playback pathprohibits inclusion of preloading interactive graphics in the subplayback path.
 2. The non-transitory recording medium according to claim1, wherein the type information indicates that the second stream isplayed back synchronously with the first stream and that the secondstream is multiplexed into the same file as the first stream.
 3. Thenon-transitory recording medium according to claim 1, wherein the typeinformation indicates that the second stream is played backsynchronously with the first stream and that the second stream ismultiplexed into a file different from a file of the first stream. 4.The non-transitory recording medium according to claim 1, wherein thetype information indicates that the second stream is played backasynchronously with the first stream and that the second stream ismultiplexed into a file different from a file of the first stream. 5.The non-transitory recording medium according to claim 1, wherein theplayback management information is classified into the predeterminedapplication media category among the plurality of application mediacategories based on a type of media of the first stream, eachapplication media category corresponding to the set of sub playback pathtypes.
 6. The non-transitory recording medium according to claim 1,wherein the first stream is associated with a first file, and whereinthe second stream is associated with a second file.
 7. Thenon-transitory recording medium according to claim 6, wherein thepredetermined number of the files readable at one time is two, whereinthe first file and the second file are different files, and wherein thesecond condition is that the sub playback path is determined so thatonly the second file is read together with the first file.
 8. Thenon-transitory recording medium according to claim 6, wherein thepredetermined number of the files readable at one time is two, thesecond file is the same file as the first file, and a remaining file isa file different from the first file, and wherein the second conditionis that the sub playback path is determined so that the second file isread with the first file and the remaining file.
 9. The non-transitoryrecording medium according to claim 6, wherein, when the sub playbackpath is a non-synchronized reading type defining that the second file isread asynchronously with the first file, the playback managementinformation satisfies a third condition that the asynchronous secondfile does not count toward the number of the files readable at one time.10. The non-transitory recording medium according to claim 1, whereinthe main playback path further includes presentation graphics.
 11. Amethod for recording on a recording medium data that can be played backby a playback apparatus, comprising: generating data having a datastructure including playback management information to manage playbackof at least two streams, the playback management information including:a main playback path indicating a position on a time axis of the firststream, a sub playback path indicating a position on the time axis ofthe second stream, and type information indicating whether the secondstream is played back synchronously with the first stream and whetherthe second stream is multiplexed into a same file as the first stream;and recording the generated data on the non-transitory recording medium,wherein the main playback path includes video data and interactivegraphics, and wherein the playback management information satisfies: afirst condition that a type of the sub playback path corresponds to aset of sub playback path types of a predetermined application mediacategory among a plurality of application media categories, and a secondcondition that the sub playback path is determined so that a number offiles readable at one time does not exceed a predetermined number, andwherein the inclusion of the interactive graphics in the main playbackpath prohibits inclusion of preloading interactive graphics in the subplayback path.
 12. The method according to claim 11, wherein theplurality of application media categories includes movies, time-basedslideshows, and browsable slideshows.
 13. The method according to claim11, wherein the main playback path further includes audio data andpresentation graphics.
 14. The method according to claim 11, wherein theplayback management information is classified into the predeterminedapplication media category among the plurality of application mediacategories based on a type of media of the first stream, eachapplication media category corresponding to the set of sub playback pathtypes, wherein the first stream is associated with a first file, andwherein the second stream is associated with a second file.
 15. Themethod according to claim 14, wherein, when the sub playback path is anon-synchronized reading type defining that the second file is readasynchronously with the first file, the playback management informationsatisfies a third condition that the asynchronous second file does notcount toward the number of the files readable at one time.
 16. Themethod according to claim 11, wherein the main playback path furtherincludes presentation graphics.
 17. A non-transitory computer-readablestorage medium storing computer-readable instructions thereon that, whenexecuted by a computer, cause the computer to perform a methodcomprising: generating data having a data structure including playbackmanagement information to manage playback of at least two streams, theplayback management information including: a main playback pathindicating a position on a time axis of the first stream, a sub playbackpath indicating a position on the time axis of the second stream, andtype information indicating whether the second stream is played backsynchronously with the first stream and whether the second stream ismultiplexed into a same file as the first stream; and recording thegenerated data on a recording medium, wherein the main playback pathincludes video data and interactive graphics, and wherein the playbackmanagement information satisfies: a first condition that a type of thesub playback path corresponds to a set of sub playback path types of apredetermined application media category among a plurality ofapplication media categories, and a second condition that the subplayback path is determined so that a number of files readable at onetime does not exceed a predetermined number, and wherein the inclusionof the interactive graphics in the main playback path prohibitsinclusion of preloading interactive graphics in the sub playback path.18. The non-transitory computer-readable storage medium according toclaim 17, wherein, when the sub playback path is a non-synchronizedreading type defining that the second file is read asynchronously withthe first file, the playback management information satisfies a thirdcondition that the asynchronous second file does not count toward thenumber of the files readable at one time.
 19. The non-transitorycomputer-readable storage medium according to claim 17, wherein the mainplayback path further includes audio data and presentation graphics. 20.The non-transitory computer-readable storage medium according to claim17, wherein the main playback path further includes presentationgraphics.